Dropbox dropping Linux - what options?

[daldred]

My Chromebook was one which recently received 'Crostini', enabling it to run Linux applications. So one of the first things I installed was Calibre, to give me easy access to my library if only the Chromebook is to hand, and to let me use it to do editing of ebooks.

No USB support yet, which is an issue, but that will come - and the Calibre server runs fine (with a Chrome app available to route incoming traffic to it), so I can get books to my ereader wirelessly while I wait for USB.

There's another issue looming the horizon, though - I use Dropbox for my library, and Dropbox are dropping (hah!) support for most Linux filesystems in November - so it looks like my library on Dropbox will need a new home.

What cloud/sync options are other people looking at for when this happens?