Check out the #artstr hash tag. Not sure if there is yet anything like those challenges but you can ask around that community. You can also start a challenge and create a hash tag for it :)

I've seen some people doing their own challenge in #art. You could do something similar in a self-starter fashion: for example 30 comics in 30 days, give it a hashtag like #30comics30days and you're good to go 😄

I'm sure others would start joining in once you've done 10 days, maybe even earlier! (doesn't have to be comics of course)

here's a cool thread I found

https://snort.social/e/nevent1qqs2nusl3zp6sv5czy46ngjq06r4xtmezr7nd98f6t6vlmy0euedm3spp4mhxue69uhkummn9ekx7mqzyzqa304ym3hfmyqh5f27aw6glqkxqsmljatdw6papqmdrytwnpaakqcyqqqqqqgjds405

Make it happen #artstr