In the Marvel Puzzle Quest R230 Release Notes (6/21/21) (https://forums.d3go.com/discussion/85226/marvel-puzzle-quest-r230-release-notes-6-21-21#latest) there is a note that states:
“When sorting characters by level, non-champion characters of the same level are now sorted by number of trained covers instead of by name.”
In my experience after updating (playing on a iPhone 7+ running iOS 14.6) this is not occurring and the default sort (by character name) is still present.