Upgrading Solitaire game on my MacBook after required computer upgrades?

FWIW, "Full Deck Solitaire" and "Solitaire Til Dawn" are both compatible with Big Sur and are available in the App Store.

Good question. Both have multiple solitaire games for free. I actually have both. I don't really have a preference. I switch between them.

Who made the Solitaire game?

Looks like they're gone from the AppStore. :(

http://www.byterun.com/gamac/