ive been using floccus for a few years now and no complaints
i havnt tried syncing tabs but i think its an option. what i do have is a one-way sync job for the tabs in each browser so i at least have a backup of them, and each browser has its own file, but i would imagine if you tried to sync the same file between multiple devices it would just get very messy at some point
raspberry pi’s arent the best option anyway since you need to add on a hat just to get some SATA ports. i think Odroid has some boards with sata connectors. zimaboard or zimablade are some other options off the top of my head