Are you aware of Pixelfed? I can't say I have any experience with it, I just know it's a decentralised and federated alternative to IG, part of the fediverse.
Does anyone know if AI trainers scrape only sites which say they do it on content uploaded, or do some of them do it on the internet as a whole? If it's the latter you may not be safe posting anywhere! At least if you post to a site that doesn't have you agree to it in their terms then you have a leg to stand on if someone does use your work for training. But then again, how would you know? It's a pickle. Best to not outright consent to it in the first place non the less.
There are platforms such as Pixiset and Pic-Time for not only posting your work but to allow people to order prints and the platform handles all the payment, printing and order fulfilment on the back end. The two I mentioned are aimed at photographers, perhaps they'll do art too, if not I'm sure there is an equivalent in the art world.
You should probably make your own site in addition to anything else at some point.