I have been told by your folks that LRF is dead. However in looking at the list of LRF that I have posted at
https://www.mobileread.com/forums/forumdisplay.php?f=126
views/downloads of one hundred or more seem to tell me that LRF is still alive and running.
Converting with Calibre (epub to LRF) will take one to four tries with a different error reported each time it fails.
It would be a wonderful New Year, if this were fixed, then Calibre would truly become the fine tool advertised.