Sitecore9.3 with identity server 6 is not working after installed the .Netcore 6.0.6 version

Question

We are using Sitecore 9.3 along with Sitecore JSS 13.0. Since Microsoft is going to end the support up to the .Net Core 5 version, we have upgraded .Net Core version from 3.1.18 to 6. To support the .Netcore6.0.6 we have upgraded the identity server 6. After upgraded we are getting error as "An error has occurred", So we enabled the log in identity server and tracked the below error.

This error is occurred whenever we are mapping the version to 6.0.6 in Sitecore.identityServer.Host.runtimeconfig.json

The same if we mapped to 3.1.0 and installed the .netcore 3.1.18, the issue is not occurring.

Did I miss any config changes or do I need to run any patch to support identity server 6 with .netcore 6.0.6 version?

'''

15:29:57] Microsoft.EntityFrameworkCore.Infrastructure [Information] Entity Framework Core "3.1.13" initialized '"PersistedGrantDbContext"' using provider '"Microsoft.EntityFrameworkCore.SqlServer"' with options: "None"
[15:29:57] IdentityServer4.Hosting.IdentityServerMiddleware [Fatal] Unhandled exception: "The type initializer for 'Microsoft.EntityFrameworkCore.EnumerableMethods' threw an exception."
System.TypeInitializationException: The type initializer for 'Microsoft.EntityFrameworkCore.EnumerableMethods' threw an exception.
 ---> System.InvalidOperationException: Sequence contains more than one matching element
   at System.Linq.ThrowHelper.ThrowMoreThanOneMatchException()
   at System.Linq.Enumerable.TryGetSingle[TSource](IEnumerable`1 source, Func`2 predicate, Boolean& found)
   at System.Linq.Enumerable.Single[TSource](IEnumerable`1 source, Func`2 predicate)
   at Microsoft.EntityFrameworkCore.EnumerableMethods..cctor()
   --- End of inner exception stack trace ---
   at Microsoft.EntityFrameworkCore.EnumerableMethods.get_AnyWithPredicate()
   at Microsoft.EntityFrameworkCore.Query.Internal.AllAnyToContainsRewritingExpressionVisitor.VisitMethodCall(MethodCallExpression methodCallExpression)
   at System.Linq.Expressions.ExpressionVisitor.Visit(Expression node)
   at Microsoft.EntityFrameworkCore.Query.QueryTranslationPreprocessor.Process(Expression query)
   at Microsoft.EntityFrameworkCore.Query.QueryCompilationContext.CreateQueryExecutor[TResult](Expression query)
   at Microsoft.EntityFrameworkCore.Storage.Database.CompileQuery[TResult](Expression query, Boolean async)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.CompileQueryCore[TResult](IDatabase database, Expression query, IModel model, Boolean async)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.<>c__DisplayClass12_0`1.<ExecuteAsync>b__0()
   at Microsoft.EntityFrameworkCore.Query.Internal.CompiledQueryCache.GetOrAddQueryCore[TFunc](Object cacheKey, Func`1 compiler)
   at Microsoft.EntityFrameworkCore.Query.Internal.CompiledQueryCache.GetOrAddQuery[TResult](Object cacheKey, Func`1 compiler)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.ExecuteAsync[TResult](Expression query, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryProvider.ExecuteAsync[TResult](Expression expression, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryable`1.GetAsyncEnumerator(CancellationToken cancellationToken)
   at System.Runtime.CompilerServices.ConfiguredCancelableAsyncEnumerable`1.GetAsyncEnumerator()
   at Microsoft.EntityFrameworkCore.EntityFrameworkQueryableExtensions.ToListAsync[TSource](IQueryable`1 source, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.EntityFrameworkQueryableExtensions.ToArrayAsync[TSource](IQueryable`1 source, CancellationToken cancellationToken)
   at IdentityServer4.EntityFramework.Stores.PersistedGrantStore.StoreAsync(PersistedGrant token)
   at IdentityServer4.Stores.DefaultGrantStore`1.StoreItemAsync(String key, T item, String clientId, String subjectId, String sessionId, String description, DateTime created, Nullable`1 expiration, Nullable`1 consumedTime)
   at IdentityServer4.Stores.DefaultGrantStore`1.CreateItemAsync(T item, String clientId, String subjectId, String sessionId, String description, DateTime created, Int32 lifetime)
   at IdentityServer4.ResponseHandling.AuthorizeResponseGenerator.CreateHybridFlowResponseAsync(ValidatedAuthorizeRequest request)
   at IdentityServer4.ResponseHandling.AuthorizeResponseGenerator.CreateResponseAsync(ValidatedAuthorizeRequest request)
   at IdentityServer4.Endpoints.AuthorizeEndpointBase.ProcessAuthorizeRequestAsync(NameValueCollection parameters, ClaimsPrincipal user, ConsentResponse consent)
   at IdentityServer4.Endpoints.AuthorizeCallbackEndpoint.ProcessAsync(HttpContext context)
   at IdentityServer4.Endpoints.AuthorizeCallbackEndpoint.ProcessAsync(HttpContext context)
   at IdentityServer4.Hosting.IdentityServerMiddleware.Invoke(HttpContext context, IEndpointRouter router, IUserSession session, IEventService events, IBackChannelLogoutService backChannelLogoutService)
[15:29:57] Microsoft.AspNetCore.Diagnostics.ExceptionHandlerMiddleware [Error] An unhandled exception has occurred while executing the request.
System.TypeInitializationException: The type initializer for 'Microsoft.EntityFrameworkCore.EnumerableMethods' threw an exception.
 ---> System.InvalidOperationException: Sequence contains more than one matching element
   at System.Linq.ThrowHelper.ThrowMoreThanOneMatchException()
   at System.Linq.Enumerable.TryGetSingle[TSource](IEnumerable`1 source, Func`2 predicate, Boolean& found)
   at System.Linq.Enumerable.Single[TSource](IEnumerable`1 source, Func`2 predicate)
   at Microsoft.EntityFrameworkCore.EnumerableMethods..cctor()
   --- End of inner exception stack trace ---
   at Microsoft.EntityFrameworkCore.EnumerableMethods.get_AnyWithPredicate()
   at Microsoft.EntityFrameworkCore.Query.Internal.AllAnyToContainsRewritingExpressionVisitor.VisitMethodCall(MethodCallExpression methodCallExpression)
   at System.Linq.Expressions.ExpressionVisitor.Visit(Expression node)
   at Microsoft.EntityFrameworkCore.Query.QueryTranslationPreprocessor.Process(Expression query)
   at Microsoft.EntityFrameworkCore.Query.QueryCompilationContext.CreateQueryExecutor[TResult](Expression query)
   at Microsoft.EntityFrameworkCore.Storage.Database.CompileQuery[TResult](Expression query, Boolean async)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.CompileQueryCore[TResult](IDatabase database, Expression query, IModel model, Boolean async)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.<>c__DisplayClass12_0`1.<ExecuteAsync>b__0()
   at Microsoft.EntityFrameworkCore.Query.Internal.CompiledQueryCache.GetOrAddQueryCore[TFunc](Object cacheKey, Func`1 compiler)
   at Microsoft.EntityFrameworkCore.Query.Internal.CompiledQueryCache.GetOrAddQuery[TResult](Object cacheKey, Func`1 compiler)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.ExecuteAsync[TResult](Expression query, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryProvider.ExecuteAsync[TResult](Expression expression, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryable`1.GetAsyncEnumerator(CancellationToken cancellationToken)
   at System.Runtime.CompilerServices.ConfiguredCancelableAsyncEnumerable`1.GetAsyncEnumerator()
   at Microsoft.EntityFrameworkCore.EntityFrameworkQueryableExtensions.ToListAsync[TSource](IQueryable`1 source, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.EntityFrameworkQueryableExtensions.ToArrayAsync[TSource](IQueryable`1 source, CancellationToken cancellationToken)
   at IdentityServer4.EntityFramework.Stores.PersistedGrantStore.StoreAsync(PersistedGrant token)
   at IdentityServer4.Stores.DefaultGrantStore`1.StoreItemAsync(String key, T item, String clientId, String subjectId, String sessionId, String description, DateTime created, Nullable`1 expiration, Nullable`1 consumedTime)
   at IdentityServer4.Stores.DefaultGrantStore`1.CreateItemAsync(T item, String clientId, String subjectId, String sessionId, String description, DateTime created, Int32 lifetime)
   at IdentityServer4.ResponseHandling.AuthorizeResponseGenerator.CreateHybridFlowResponseAsync(ValidatedAuthorizeRequest request)
   at IdentityServer4.ResponseHandling.AuthorizeResponseGenerator.CreateResponseAsync(ValidatedAuthorizeRequest request)
   at IdentityServer4.Endpoints.AuthorizeEndpointBase.ProcessAuthorizeRequestAsync(NameValueCollection parameters, ClaimsPrincipal user, ConsentResponse consent)
   at IdentityServer4.Endpoints.AuthorizeCallbackEndpoint.ProcessAsync(HttpContext context)
   at IdentityServer4.Endpoints.AuthorizeCallbackEndpoint.ProcessAsync(HttpContext context)
   at IdentityServer4.Hosting.IdentityServerMiddleware.Invoke(HttpContext context, IEndpointRouter router, IUserSession session, IEventService events, IBackChannelLogoutService backChannelLogoutService)
   at IdentityServer4.Hosting.IdentityServerMiddleware.Invoke(HttpContext context, IEndpointRouter router, IUserSession session, IEventService events, IBackChannelLogoutService backChannelLogoutService)
   at IdentityServer4.Hosting.MutualTlsEndpointMiddleware.Invoke(HttpContext context, IAuthenticationSchemeProvider schemes)
   at Microsoft.AspNetCore.Authentication.AuthenticationMiddleware.Invoke(HttpContext context)
   at IdentityServer4.Hosting.BaseUrlMiddleware.Invoke(HttpContext context)

'''

Answer 1

It's not really clear if you try to upgrade Sitecore Identity (which uses Identity Server), but based on the Stack Trace it seems that you are. Sitecore Identity is based on IdentityServer4. There are some big differences between IdentityServer4 and IdentityServer v6.

It seems there is an upgrade path from IdentityServer4 to IdentityServer v6, but I'm not sure if this also works for Sitecore Identity: https://docs.duendesoftware.com/identityserver/v6/upgrades/is4_v4_to_dis_v6/

Sitecore Identity is based on IdentityServer4, but is still a custom implementation. I'm not sure if it's possible to just upgrade that. It might be better to contact Sitecore support and ask them if it's possible.