Hell I've had magazine deletion requests sitting around for months, since before ernest disappeared lol.
I run @SquaredCircle here and with all this never-ending breaking I've been spending the last 3 days testing out Federation between 4-5 other lemmy and mbin instances trying to find a place to move my account and the community as a whole.
Magazines can be deleted. There is a Delete Magazine button in the Magazine Panel of any magazine you own (on the General tab, first one).
However at this time it does not appear to be an automatic thing (I believe Ernest has to clear then manually). I've deleted around a dozen so far (which were taken care of within 24h) and have had over a dozen more as well waiting for deletion (which have been sitting there for a month+ as Ernest has been busy as of late, and then the holidays and such).
If you didn't get an answer elsewhere yet: You click the button and it sits pending until approved (whether its Ernest approving manually or an automated batchjob I don't know). Seems to be once a day or so, so could be either but that's just anecdotal. That's it tho. Click the button and wait, no other steps lol.
Either way, once approved the magazine will just appear in your moderated list on your profile (no notification or anything from what I've seen) and from there it's yours to do with as you want. I've claimed a dozen or so over the last day or so to delete (unused ones people sat on).
1 part 'Meta users 'already have' an account so getting into it is easy', mixed with 1 part 'The slightest possibility of inconvenience (like having to choose a Mastodon server) acts as a deterrent to most people when alternative means are available'.