IMHO, square taper is about as sImple and foolproof as you can get. Won’t even bother to count how many I’ve owned, worked on or moved on to another owner, but easily in the dozen of dozens. In other words, if you can’t make it work with square taper, the last thing you need is a more complex and difficult to find interface.

Would suggest you either find a local experienced mech who can show you how to install square taper stuff (why do you need to remove the crank so much that it expands, anyway? Why has your puller ‘seen better days’?. Yet more questions…) or go directly to currently available hollowtech. Any 9-10-11 speed hollowtech will work just fine with 8 speed.

Install it, enjoy it, and leave it the heck alone.