Cheese has an initiative to port to GTk4 and possibly libadwaita. Progress on this appears to be slow.
Are there any other apps? @GrindamN has pointed out using guvcview which looks and feels more feature filled without complicating things. Would have been nice an option to integrate the video window within the settings part.
guvcview is from a project on sourceforge - its ticking along nicely with bug fixes on a regular basis - no major updates for a number of years though.
Think guvcview is a strong candidate to replace cheese unless anyone else has done an indepth analysis for another candidate.