Push subscription managers is a new user group introduced by the MediaWiki extensionEcho within August 2020.
According to the commit message, it will "allow privileged accounts to purge expired subscriptions from the database on behalf of other users." "This right will be granted to a bot account on metawiki associated with the Wikimedia push notifications service, and thepush notifications service account will make push subscription delete requests to the API for subscriptions for which vendor APIs return bad subscription responses."[1]
This group should exist only on Meta-Wiki. Errors have caused it to appear on other Wikimedia wikis.[2][3][4][5]