Self-hosting has other drawbacks. Your need to maintain your server, you need a steady internet connection and a steady power supply. These are things providers like Proton and Tuta deal with for you.

Unfortunately, no iOS app… looks cool though

Does not answer your question but I just checked and you cannot customize the font in Mlem

Mlem for iOS let‘s you filter for keywords

Unfortunately, it uses the Bing search index. Would have loved a search engine truly independent from American tech companies.