[the4anoni]

Thanks for all the recommendations

I found a few more Pocketbook apps

RemoteInk - use Pocketbook reader as Monitor
VNC Client
Nextcloud client
Pocket Client
Syncthing for Pocketbook
Text Editor (requires BT keyboard
Tetris
RSS and Atom Reader
Tic-Tac-Toe
ZIM reader
Custom Dropbox client
Pocketframe - Digital picture frame from the old PocketBook e-reader

I have also found 2 useful plugins for KOreader

Pocketbookcover - Automatically updates the book cover which is displayed when the Pocketbook device is turned off.
A Pocketbook app that sync the reading status between KOReader and Pocketbook's original software.