Here's what browsers I've tried and the results:
brave ok, firefox ok, librewolf fails, konqueror ok, chromium ok
So it would seem, that librewolf is the culprit, just started using last week and that would explain the errors.
I did make an attempt at the serving up the java, placed the script at /usr/share/tvheadend/src/webui/static, it does ask for user/password, but then nothing occurs, just a blank, tried with all the browsers.
A related question, why this particular db, other than "its always been used", seems as very specific to TVH, and to have to compile, just to get a db dump and see whats there, when there are other db's that do the job?
I'll wait a couple days, and file a bug report, on the errors with epgdump.
Thanks for the assistance and pointers, much appreciated.