Yes, I'm running LUKS encryption on top of my BTRFS partition
Right, I'm not an expert on this, but I've learnt there's no better way to learn, than to be wrong on the internet.
LUKS is a full disk (or full partition at least) encryption system. Surely the filesystem (BTRFS in this case), is on top of LUKS, not the other way around? After all, if I run
blkid then it tells me that the encrypted partition is
TYPE="crypto_LUKS", instead of
Contrarywise, as far as the running OS is concerned the filesystem is vanilla ext4, so I don't see why Dropbox would have a problem running on it. Indeed, I've yet to get a warning from Dropbox on any of the machines I'm responsible for, most of which are using ext4 on top of LUKS.
Still, I don't see why Dropbox can't continue to work on any file system with extended attributes, especially as it's been working on (eg) BTRFS systems already.