Remarkable

If you're just looking to make a backup of the entire tablet at once, and you don't need the backed-up files to be usable for anything on the computer (other than being able to restore them back to the tablet when/if needed) ...

• You can use rsync or scp to just plain copy the files from the tablet. My rm2-backup script does this, using rsync, plus it stores the backed-up files in a way that files which didn't change from the previous backup are not copied again, they are "hard linked" to the same file in the previous backup - so if you've only edited one document, it might only download 15-20 files, but the directory it produces will still be a full backup of the entire tablet.

  The Filesystem page on the same site has more information about how the tablet stores documents, and why you can't "just download them" in a format that the software on your computer can deal with.

• You can use RCU to back up individual documents to .rmn files, which can later be uploaded back to a reMarkable tablet.

  I've heard that RCU also has a command line interface to do this without having to use the GUI, but I haven't used it myself - mostly because it takes forever to start. Just running ./RCU --help takes 16 seconds on an M2 MacBook Air, which IMHO is "not great but not horrible" for a GUI program, but is a deal-killer for command line utilities which might be called from a script. (I understand why it takes so long, and I don't disagree with doing it that way, it's just ... as a user it's kind of irritating.)

• I am working on a Perl script which can download the same .rmn files that RCU creates, and which has an option to download all documents at once. It isn't ready yet, mostly because I haven't had time to concentrate on it, but I have gotten as far as producing files that RCU is able to upload into a different tablet. (Plus it doesn't take 15+ seconds just to start up.)

  I want to finish it, then I want to re-write it in Golang so people don't have to deal with figuring out how to install Perl modules just to use it.

If you need the backed-up files to be usable (i.e. all files converted to PDF, with pen strokes "burned into" the PDFs and therefore not edit-able if the PDF files are uploaded back to a tablet), you can ...

• use the built-in web interface to export them as PDF files.

• use the reMarkable apps, if the tablet is connected to a cloud account. (I'm pretty sure they can export documents to PDF, but I've never used them so I can't say for sure from direct experience.)

• use RCU to download them to PDF files.