I have been using the filen.io cloud storage service for around a year; mostly as a virtual rclone mount HDD for my VPS. Filen is supposed to be a privacy oriented cloud storage service like dropbox or megaupload and is based in Germany.
They do have an almost-native ARM Linux GUI .deb, the almost part being that on a Librem 5 you need to use the compositor to shrink the UI down, with a little rotation I have been able to get access to all of the buttons and features of the desktop designed UI. The app also allows you to mount a network share and set up backups. There is also a CLI access program as well as being included as an option in the newest rclone.
Speeds could be better lately though they say it is related to big black friday signups and hardware shortages.