I never had data outright vanish, but similar to the comment you replied to, it was just unreliable. I found Syncthing much more useful over the long haul. The last 3 times I've had to do anything with it were simply to manage having new machines replace old ones.
Syncthing sadly doesn't let you not download some folders or files, but I just moved those to other storage. It beats the Nextcloud headache.
Oh no worries, yeah that works like gitignore, I’m talking more like how Nextcloud and Dropbox let you like, have a list of folders and checkboxes where you can be like “this machine doesn’t need my family photo collection synced to it” kinda thing. Which to my knowledge syncthing doesn’t have.
“This machine doesn’t need my family photo collection synced to it” is .stignore. It’s a bit confusing because .stignore is more like .git/info/excludes than .gitignore in that it’s not synced between machines[1]. (If you wanted a synced ignores file then you need to #include that file from each machine’s .stignore manually.) And what’s ignored on one machine doesn’t then need to be ignored on the others, which will still sync it between themselves in that case. So no pretty checkboxes, but echo /Photos >>.stignore on the machine in question and you should be good (including to delete the Photos subdirectory on that machine).
Syncthing sadly doesn't let you not download some folders or files, but I just moved those to other storage. It beats the Nextcloud headache.