Remarkable
Transferring files, PDF and epub
To transfer files through USB you need to connect the USB port, then in Settings -> General -> Storage -> activate USB connection.
You will be able to connect through http://10.11.99.1/ using a browser to upload files, but files are limited to < 100MB.
You can find all IP addresses and username + password to SSH into the Remarkable through
Settings -> Help -> Copyrights and Licenses -> General Information -> under GPLv3 Compliance (on the right )
Transfer everything into the /home/root folder. Other folders get deleted on OS upgrade.
After transfer PDF / epub files won't show up because they need to be stored in a specific place and have .metadata, .content and .thumbnail files generated.
https://www.informaticar.net/how-to-transfer-files-to-remarkable-paper-pro-without-cloud/ has a description of the script you can run in linux / windows with linux subsystem. Script can be found https://github.com/adaerr/reMarkableScripts/blob/master/pdf2remarkable.sh
Resources
https://remarkable.guide/ - replaces the old wiki
https://www.davisr.me/projects/rcu/ Remarkable Connection Utility (paid)
https://support.remarkable.com/s/article/Using-reMarkable-without-a-subscription Using Remarkable without a Subscription