Turns out that the Opera Mini proxies still can be accessed from Opera Mini 7.1 on an Nokia E6 (Symbian Belle), and Opera even still supplies the download. Can't get Opera Mobile 12 from them anymore though, but it's available from some download sites that seem only marginally more shady than the Symbian software sites 10 years ago...

(Ok, I certainly still have it somewhere in my archives too, but searching the web seemed easier...)

Anyways, added three user agents to the uadb 😉