you found..

LackeyCCG

a free card game engine(?/player? wtf would you call it)

its pretty versatile as you can play basically any card game online through plugins

LackeyCCG lackey forums

about page through wayback

(the navbar is broken on the live version of the site)

i mainly use it for mtg, its so fun not being limited by either paywalls (:mtgo) or shitty clients (with shittier paywalls: arena). you can literally pick it up and play any game or deck for a specific game. the """"downside""" is nearly nothing is automated, so its as close to playing paper as possible, though this really isnt even a downside honestly

here's the mtg plugin i use and its forum thread

it also gets bonus points for the ancient shitty gui which i absolutely love