Same issue. Opera 72.0.3815.207 and Opera Dev 74.0.3862.0, started happening yesterday.
Workaround 1: just type anything fast enough and hit enter to get your SE to load up so you can finally safely type for any amount of time both in address bar and search box.
Workaround 2: duplicate any already open tab that works, proceed with your search.

Same issue. Opera 72.0.3815.207 and Opera Dev 74.0.3862.0, started happening yesterday.
Workaround 1: just type anything fast enough and hit enter to get your SE to load up so you can finally safely type for any amount of time both in address bar and search box.
Workaround 2: duplicate any already open tab that works, proceed with your search.

OPR/42.0.2374.0 here, still no fix. Really annoying bug/feature.