Updated my 7t to OS 12 last week. It made my phone incompatible with my carrier, Visible Wireless (a budget version of Verizon). I specifically bought the 7t two years ago because it was compatible with Visible.

Switched to Mint and having mixed results that I am fairly confident is due to similar compatibility issues. Aside from all the other reasons to drop OnePlus, I'm switching to a pixel because it's just not popular enough to have promised compatibility.