I just received my reMarkable 2. Have not tried to connect it yet to my Linux PC.
They do support transfering files when connected with USB, but it is through an Web UI.
https://support.remarkable.com/hc/en...-cable?preview[theme_id]=210292689&preview_as_role=anonymous
It is a shame that they don't support Linux the same way as Windows and MacOS. Considering that reMarkable is running a Linux OS.