Yes; I've been using Dropbox with btrfs on Arch Linux for a month or two now. According to the Arch wiki[1], Dropbox added support back for ZFS, ecryptfs, XFS, and btrfs a little over a year ago (around seven months after they initially dropped support for everything other than ext4 on Linux). That being said, I had been using Nextcloud on a DigitalOcean droplet for a couple years before that, and I never had any issues with it. The only reason I switched back to Dropbox was that Google announced earlier this year they were getting rid of Google Play Music, and I had a bunch of music uploaded from CDs on there that I wanted to back up, and I would have ended up needing to pay more per month for the storage on a DigitalOcean instance to fit all the music than the $10/month that Dropbox charges for 2 TB.

[1]: https://wiki.archlinux.org/index.php/Dropbox#Using_Dropbox_w...