To just play:
https://codenames.game/ (just a fun game, 4 player)
https://playingcards.io. (free card games online)
To create play:
www.twinery.org (for narrative games)
www.Renpy.org (for narrative games)
https://www.photopea.com/ (free alternative to photoshop)
www.Opengameart.org (source for images and other media)
https://flippity.net/ (shortcuts for making learning games)
https://www.wisc-online.com/ (pre-made digital games, teachers can just input their questions)
https://freesound.org/ (to grab free sounds)