I updated to 8.0 using local update. I first factory reset the phone, then ran the update from the recovery menu.

After the update my mobile connection is stuck in 3G mode, instead of 4G.

Hi there. You have to perform a factory reset also after the Oreo update.

Hi,

1. Really? A factory reset after installing the update on a factory reset phone? Does the update itself leave files around that it shouldn't?

2. I apologise, but it appears that 4G works. Either my provider had problems, or something changed in the algorithm that determines availability, because when I left the house the 4G connection turned back on. So you can close this thread.

Yes, a factory reset is highly reccommended after EACH update. Glad you have solved your "issue".