I've been searching around at,
https://pgaskin.net/KoboStuff/kobofirmware.html (which is a great site. Thank you Peter Gaskin) for some older firmware ever since I choose to revert back to older firmware. I've had my Clara HD for a couple of years now, but I can't remember which firmware versions had the biggest changes? Which ones actually made any difference in terms of speed? At which point did the option to reset reading stats disappear from the "energysaving & integrity menu"?
If anybody can remember which versions brought the biggest changes, please feel free to make a contribution to an overview below! Or is this information available somewhere?
Edit: sorry about the embarrassing bad spelling in the heading