Sounds like you want Cockatrice: https://cockatrice.github.io/

The rules aren't embedded into the client; it's "just" a virtual tabletop where you enforce the rules the same way you would playing with a friend in person. Cards have to be imported but it's fairly automatic (basically just clicking a few buttons after startup), so you could either only import the sets you want or just not use the ones you don't want (which is also how it tends to work when playing informally in person; it's not like you usually have a judge to enforce that you or your friends are playing by whatever rules you agree to).