Sad news that Roger Hui has passed away on October 18, 2021.
All I have so far is a reference to this at Dyalog:
https://www.dyalog.com/news/148/420/Roger-Hui.htm
I never met Roger Hui even though I worked at I.P.Sharp many
years ago (around 1972-1976) but Roger was an admirable force
in the world of APL and of course J.
Condolences.