It’s not the adhesive around the display that has loosened; it’s the swollen battery pushing it out.

Replace the battery, then glue the display back.

As long as sideloaded apps follow the same sandbox model as approved apps, I am not against it.

It seems that Sierra Wireless 3G modems are the last WWAN drivers built into OSX.

Later releases did not add drivers for LTE modems, and all WWAN support has moved to Instant Hotspot with iPhone.

I use AdGuard, with Safari extension and DNS filter.
For ads embedded in the app, DNS level blocking might be the only choice on iPhone.