Cheers guys, this thread got my 10th gen paperwhite v5.16.2.1.1 running kual + koreader.
My process was:
1) follow languagebreak instructions.
2) copy kual-mrinstaller-1.7.N-r19298 folders to root
3) install JailBreak-1.16.N-FW-5.x-hotfix via log mrpi
4) install KUAL-coplate 5b5d1d2-20231104 via log mrpi
It moans about ro filesystem errors but works anyway.
5) install koreader-kindlepw2-v2023.10
Many thanks