Discovered a new digital CCG the other day that I've been having a blast with that I thought others around here might enjoy:

https://wordbots.io/

Most people who play CCGs like Hearthstone and Magic seem to enjoy coming up with custom cards too. In Wordbots, you actually get to play with the cards you create. I've only created a few cards so far, and the parser that reads your card and tries to do what it says is a little finicky, and it sometimes takes a little work to find wording to get the card to do what you want, but the developers have been responsive to my questions on Discord with suggestions on how to word cards to get the effects I want.