I used to use xbrowsersync [0] for cross-browser sync and rn I'm using raindrop [1]. Xbrowsersync is self-hostable, but raindrop is not. Both are FOSS.

There's also a big list of different projects here: https://github.com/awesome-selfhosted/awesome-selfhosted#boo...

[0] https://www.xbrowsersync.org/ [1] https://raindrop.io/