.NET Core creates AspNet tables incompatible with .NET Framework 4.5

Question

From an ASP.NET MVC project (on .NET 4.5) I created a SQL Server database (and security using Microsoft.AspNet.Identity.EntityFramework.) using EF and the Package Manager. So far so good.

A few years later, now, I created another project using Blazor on .NET 5 and EF Core and implemented the security using Microsoft.AspNetCore.Components.Authorization and Identity.

The problem now is that I need both programs to access the same database but Blazor / .NET 5 errors on LogIn saying that there are invalid fields. I compared both tables and I can see that the AspNetUsers from .NET Core has additional columns, and so the AspNetRules which I also use.

I cannot rebuild the ASP.NET project in .NET Core because it uses old 3rd party libraries. Is there a solution?