You know, this would be far less of an issue if Apple offered some way of downgrading iOS...

I thought you can do that with iTunes if you just get the signed old ipsw file. I remember reverting from iOS 11 to 10 this way

Similar issue with the 6S happened when ios 11 was released. In that case Apple DID allow people to downgrade (back to 10.3.3 in fact!). I don't have a third party screen, but I did take advantage of that and tried ios 11 for a while. Eventually went back to 10.3.3 before that window closed (they fixed the issue with 3rd party screens on 6S).