Tabletop Simulator-like

Tabletop Playground - TTS clone, commercial but with a wider variety of games? (claimed). Can import TTS games afaik. Games can be found here

Tabletop Club - FOSS TTS clone, not sure how far along? can not import TTS games atm

Vassal - FOSS, originally developed for tabletops afaik, older but actively developed and huge selection of modules (though still w focus on deeper/wargame-like games).

OCTGN - full game engine but I only know it from ppl playing Android Netrunner on it

Web-arenas

virtualtabletop - free, no official game art etc but works without signup!

boardgame arena - freemium, many games

boardzilla - FOSS, no signup required. Very limited selection of games currently (basically 7WondersDuel, PowerGrid and 7 others) but nice that it exists!

tabletopia - a huge selection (2500+?) but very freemium, I think moreso than bga

Mostly - FOSS but mostly 'classic' card games (Doppelkopf, Bridge, Skat, ...)