Awesome build! The switches look neat!
I made the mistake of not getting a kit when building my TBK mini with per-key RGB. Hand-soldering what feels like hundreds of connections between MxLEDBits is not fun :/
Enjoy your keeb, it looks amazing! How is the trackball sensitivity btw?
Maybe take a look at Komga. It does support both ebooks and graphic novels, has koreader sync for progress and can even share/distribute stuff via OPDS to koreader and other clients that support OPDS.
However file uploading is not directly possible, maybe this would work with something like a Nextcloud server?!