I had the requirement for the same basic functionality and switched to Syncthing several years ago. Haven't looked back: works all the time, every time, and it is much easier to maintain.
I use syncthing and nextcloud. Syncthing just as an easy way to drop things between phone and computer. The ~$5/mo Hetzner nextcloud instance for my Zotero backup, occasionally sharing/soliciting files from friends, and a few not so important backups (that I've been meaning to mirror to b2).
It's basically fine but I can imagine the more advanced features not working so well. It has been on my list for years to add recurring task support to nextcloud tasks but it's a pretty big effort since I'm quite unfamiliar with the stack and there is a decent refactoring needed before the feature can be added.
