I wrote https://github.com/ScottESanDiego/gmail-api-client to work around this, using exim and fetchmail to get things into #gmail . It's working REALLY WELL so far, with all the usual filters and stuff, just as when using #gmailify .
Problem is that it uses "restricted" API calls which means annual code security reviews which I'm not going to do ($$) OR renew the auth every seven days. My app is "in production" so the token isn't expiring, not sure what happens when I fail to do a code review.
@nelson @jmason after the nightmare that was fetchmail vs. Gmail OAUTH 2.0, I gave up and just forward gmail to my ISP account. But thankfully gmail was never anything other than a place to trap notifications from FB and that sort of crap I don't care about, anyway.
https://billauer.co.il/blog/2022/06/fetchmail-gmail-lsa-oauth2/