Same, I really wanted to share history, but when I realised I was going to need to send things to a remote server I instead wrote a tiny script to search through backups that are shared across machines by Syncthing.
I just search over $BACKUPS/*/latest/local/share/fish/fish_history with grep and skim
Nice solution
Atuin offers a self-hosted backend server for syncing, so you don't need to trust anybody