I've personally been a fan of Pretend You're Xyzzy (http://www.pretendyoure.xyz/zy/) and CardCast (https://www.cardcastgame.com/) as far as online CAH goes. The design on PYX is.... modest, to say the least, but the custom decks feature is a killer app. Great for community games.
Was about to unfeature this because it looked like pirating, but it's actually fine since the original game was released under a Creative Commons license. Interesting!
Looka
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Accidental Tech Podcast - Uncomfortable in My Pants