Changes theme immediately upon install, but despite having a setting that suggests it'll change every x minutes, this does not seem to be the case.
Will it change every 60 minutes? I guess one has to wait 60 minutes to find out.

It's vibe-coded, as seen by the description going
'Bring variety and freshness to your browsing experience with [Extension Name]!'

as for its 'future features'
"Customize your rotation with theme favorites, schedule time-based changes, or adjust the rotation interval."
it hasn't been updated in 7 months.