Sorry if this has been asked before, but I couldn't find it if so. How can I remove the obsolete APIv4 extension cleanly? There's no disable or uninstall uption on the Extensions page. Thanks.
I would delete the extension folder from the extension directory.
You may need to run the below query to delete the entry from the extension table or sometimes it should delete automatically when you will hit refresh button on extension page
DELETE FROM civicrm_extension WHERE full_name = 'org.civicrm.api4';