Is there anything about Startmail (company that does Startpage.com) that is worth avoiding? I’ve never paid for mail but if it’s solid and avoids Google I might.

Agreed, you could pick your own algorithm(s) to follow just like hashtags, maybe just a “follow this hashtag and similar engagement posts”. It might be an easier transition from the imposed monolithic algorithm God that meta/google impose if people are in control of how the app feeds them.