I was recently learning to play go using gnugo[1].
to learn contract bridge, I find the bcalc single/double dummy solver bcalc useful: http://bcalc.w8.pl/index.php?lang=en&topic=download
also good is the freeware bride program Wbridge5, which has won several world computer bridge championships. It is a Windows program, but runs fine on linux with the wine emulation layer. (I've run it on fedora 30, debian 10 and ubuntu 19.10)
to learn chess, there's scid and the stockfish engine included in distros such as debian and ubuntu.
There's also the lc0 engine, which is the open source version of the mighty Deep Mind AlphaZero chess engine - linux installation instructions for lc0 are here: https://github.com/LeelaChessZero/lc0/blob/master/README.md
To learn auto racing or acrobatic flying, there's the esports for engineers package of classic PC simulation games: https://github.com/bencaddigan/esports-for-engineers