I got caught the same way with an impulse buy of an A1 Mini/AMS Lite last fall. I’m still running the 1.04 firmware and Orca Slicer on LAN mode for several months now with little issue, (sometimes it drops the LAN connection on start up and needs to be manually reconnected). If you do upgrade to the evil firmware and don’t like it, Bambu currently does let you downgrade to an older firmware and you can go back to a safer firmware.
Most of the Bambu users I have interacted with don’t care because they want to run their printer from the Bambu Handy app. And if you want to use the Handy app, you can’t use LAN mode because you need to be logged in. But I don’t like using my phone for such things anyway.
Prusa Core One with MMU or Qidi Plus 4 and the Qidi Box. The Qidi Box is at the pre-sale point now. They have been taking things slow with their AMS unit. Either printer is affordable and in the size range you want. Both are corexy, Qidi run Klipper and Prusa runs Marlin firmware. Both brands have heated enclosures to make printing fussier filaments easier. And PETG definitely benefits from that.
If I was starting over and wanted a larger printer, it would be a coin flip choice between those 2 printers.