At least on lemm.ee, that is a setting in user settings. Look there.

Edit: misread comments as posts. Hope it still helps though.

Sadly, I haven’t found a way to do it. It would be a great feature

If you browse in an app on your phone, most of them support default sorting. I think some of the alternate UIs might do as well such as old.lemmy.world, a.lemmy.world, etc.

It’s an option in liftoff if that’s any use to you.