My port of XTerm stopped working with 5.3 firmware. Instead of trying to revive it I took another way. I wrote a very simple GTK+ terminal emulator based on VteTerminal library.
It is available for testing here
I run it successfully on KT 5.3.2 firmware. I hope it will also work on PW. It is reported to run fine on Paperwhite.
I believe it should also be compatible with 5.1 firmware.
Any feedback welcome