I do not know the device. There is a general rule in Android, “Never go back”.
Just to help you rule things out, I would say that an Over The Air update must be safe to perform, so it should throw an error if it is being used for anything which is a downgrade.
Most devices where you want to downgrade, you are going to be looking for an expert or even “engineer’s” solution, that is rather than an Upgrade operation carried out in user space such as Recovery and I would say (most) adb operations.
Generally one would search for a Fastboot ROM specified or recommended to carry out the intended downgrade.
Many users having accepted an upgrade just wait for /e/OS to catch up to that Android version.
Note this thread starts several months ago Official /e/OS builds for Nothing - CMF Phone 1 (tetris)
Do you feel the question in Post #57 is a bit like yours ?? The response of the wise Edit, cautious (??), seemed “don’t do it”.