I bought a Remarkable 2 tablet a while back. I quickly realised two things -
1. Remarkable's own software is a steaming pile of poo. Their inbuilt web server for uploading files is extremely buggy and unusable. It's dog slow. You can't try to drag many files in one go, or it crashes. You can't try to upload a large file, or it crashes. There is also a hard limit on the file size you can upload (something like 100MB) which makes it unusable for some heavy PDF files I have. They push you towards paying for their cloud service subscription, which I will never do, just to be able to sync files. There is also no way to just ssh files over because their pdf reader will refuse to read them. All I want is to connect the remarkable every day for a few minutes to my computer and have it sync my files, and there is no way to do that.
2. Most of the "hacks" online are written assuming that you can install toolchains like Toltec on the device, and they are NOT updated for the newer firmware. My remarkable came with 3.15 and while there are some instructions on how to downgrade the firmware before installing the toolchain, they never worked for me. So I stuck with the subpar software and reading experience...
... until I discovered [ReManager](https://github.com/rmitchellscott/reManager). It just worked out of the box, did not require a firmware update, and I was able to install KoReader and other goodies (such as some launcher improvements). It can also transfer large files easily. What's ironic is that KoReader can read djvu files, which removes my need to use large PDFs in the first place. Equivalent djvu files are much much smaller.
Thanks to everyone in the remarkable community who contributed to ReManager and other assorted remarkable hacking!
EDIT: Also must point out a cool thing that I discovered recently - ReManager comes with a one click installer for the Zig toolchain on the Remarkable 2! It is slow, but I was able to compile and run zig programs on the tablet.