This is a very good point that slipped my mind. Thank you!

I've got the fairphone 3+ running /e/ os and T-Mobile is the carrier. It works pretty well and I don't have many complaints. Keep in mind that the FP 3+ only connects to 3G and 4G networks while I believe the FP 4 connects to 4G and 5G networks so I don't have any experience using 5G. I'm sure it would be fine unless you have any specific reason to doubt that Verizon would work.