Fedora, it fucking slaps and worked right out of the box. I'm using it for work and play on my main rig! I dual boot for some very specific hardware things that are not normal, but other than that it's been seamless! When I booted into Windows 10 again, they auto installed copilot... Glad to be done with this crap.
looks like rclone supports box.com! I never used it for that but rclone is a real gem; give it a shot. You might need to set some time aside to RTFM but it's time well spent because it has such wide compatibility and works basically the same way for all the services. once you know it, you know it.
might not suit your use case but if you are looking for a free file sync service to get away from box.com, disroot.org has a nextcloud instance among various other services. i have used them on and off for years. nextcloud uses webdav.
Strongly seconding rclone. It's an amazing tool for turning the usual crap-security crap-privacy cloud storage into genuinely useful offsite storage.