I’ve discovered CardGames.io when I found out that the author [1] of one of Firefox addons I use, Redirector, passed away. It’s a pretty straightforward, lightweight web app by the same author, with a bunch of card games (and some non-card, too) to play online. Here’s a blog post about the beginnings of CardGames:
https://einaregilsson.com/story-of-cardgames-io/Today I’ve discovered that it keeps getting updates!
[1]: https://einaregilsson.com/