is there anything reasonable to sync browser bookmarks and history across devices that can be self hosted and integrates with firefox on desktop and on ios?
There are some extensions that do this, unfortunately due to iOS browsers all being Safari under the hood there are no WebExtensions on Firefox iOS, which means solutions like xBrowserSync won't cut it for you.
Regular Firefox sync is E2EE, and can be self-hosted but it's a bit yucky to do, so that may also not be worth it to you
Right, I'm remembering now that self-hosting FFSync ALSO wouldn't work because the URI is hardcoded on iOS because safari 