Turns out this can also happen in cases when your package doesn't support your solution.

In my case, I had a .NET 8 project:

  <PropertyGroup>
    <TargetFramework>net8.0</TargetFramework>
    <Nullable>enable</Nullable>
    <ImplicitUsings>enable</ImplicitUsings>
  </PropertyGroup>

I was trying to install Microsoft.AspNetCore.Authentication.JwtBearer version 9.0.1, which is only compatible with net9.0.

The solution? Install the 8.0.12 version of the package instead. Problem solved.