Hear me out; here is a place I feel like an on-device machine learning model would make a Mastodon client dope:
Say you see a post you don’t like (like w/non-content-warned photos of spiders). It’d be neat to be able to hit a button to “filter posts like this.” That could use some text parsing of the post and alt text to propose topics/phrases to add to filters. And since filters are a Mastodon feature accessible via the API, they’d end up filtered server side going forward.