Yes, I found it confusing too - but installing the beta on my Windows machine (using the same database server) works just fine.

Will paste the stacktrace below:

System.InvalidOperationException: Unable to convert user ID to int ---> System.InvalidCastException: Unable to cast object of type 'System.String' to type 'System.Int32'. at Umbraco.Extensions.ObjectExtensions.TryConvertTo[T](Object input) --- End of inner exception stack trace --- at Umbraco.Cms.Core.Security.UmbracoUserStore2.UserIdToInt(String userId) at Umbraco.Cms.Core.Security.BackOfficeUserStore.FindUserAsync(String userId, CancellationToken cancellationToken) at Umbraco.Cms.Core.Security.UmbracoUserStore2.FindByIdAsync(String userId, CancellationToken cancellationToken) at Microsoft.AspNetCore.Identity.UserManager1.FindByIdAsync(String userId) at Umbraco.Cms.Web.BackOffice.Install.InstallApiController.CompleteInstall() at lambda_method271(Closure , Object ) at Microsoft.AspNetCore.Mvc.Infrastructure.ActionMethodExecutor.TaskOfActionResultExecutor.Execute(IActionResultTypeMapper mapper, ObjectMethodExecutor executor, Object controller, Object[] arguments) at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.g__Awaited|12_0(ControllerActionInvoker invoker, ValueTask1 actionResultValueTask) at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.gAwaited|100(ControllerActionInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted) at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Rethrow(ActionExecutedContextSealed context) at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted) at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.InvokeInnerFilterAsync() --- End of stack trace from previous location --- at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.gAwaited|240(ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted) at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResourceExecutedContextSealed context) at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted) at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.InvokeFilterPipelineAsync() --- End of stack trace from previous location --- at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.gAwaited|170(ResourceInvoker invoker, Task task, IDisposable scope) at Microsoft.AspNetCore.Routing.EndpointMiddleware.gAwaitRequestTask|60(Endpoint endpoint, Task requestTask, ILogger logger) at Umbraco.Cms.Web.Website.Middleware.PublicAccessMiddleware.InvokeAsync(HttpContext context, RequestDelegate next) at Microsoft.AspNetCore.Builder.UseMiddlewareExtensions.<>cDisplayClass61.DisplayClass61.

I first tried using a Linux SQL Server instance running in a Docker container (failed with the same error) but then moved over to a SQL Server Express 2016 database on our (Windows) development server. All databases were empty at the point of Umbraco installation and connected to from Umbraco using the SA account. The Express databases were created using SQL Management Studio Express.

It feels like I followed the installation instructions pretty closely to what Warren's doing here: https://www.youtube.com/watch?v=lDL9tsJojfs However, I'm still on Catalina if that could be a factor.

I have no idea if or how that should be the problem.. Based on the stacktrace, it should be the same as executing this code.

"-1".TryConvertTo<int>()

Are you somehow able to execute similar code in a simple example?

Maybe as first thing in public static void Main(string[] args)? And then maybe you can debug and see what is going wrong?

Personally I can only test on windows and ubuntu

Just as a heads up: I just tried installing the RC on the same mac and it resulted in the same crash as earlier. I also did try to make a new console app (adding the Umbraco.Cms package and a reference to Umbraco.Extensions in the code) and execute the code you quoted above. That worked just fine, no error at all, so the problem does not look like it's in the extension method.

Unfortunately I don't have access to another Mac with a more recent OS to see if it's something weird on my machine or if it is indeed a macos related problem.