Just thinking about updates - I can understand that the prospect of porting the entire mod would be daunting considering all the cool stuff in it but how about just working on a few elements for us to play with?
Personally I'd vote for:
Handy bag + cards
Memory chests
Both would be distinct and invaluable in 1.16.5 and the rest would be as you see fit. There seem to be a fair few 'popular' mods that have done this as certain features have not yet been implemented in the newer versions.
Just a thought - keep up the great work!

I so miss this mod in my latest minecraft packs.. The handybag, inventory changes were absolutely brilliant and one of a kind...

Updates are planned, it's just a matter of having the time to do it, as I've mostly been focusing on some other mods in recent years. And also when I do the port, I'm likely going to be mostly rewriting the mod at the same time, as there is lots of old code that can use a good clean-up. Not to mention lots of usability issues for example with the messy modifier key combinations to toggle features of various items.