I am also from Poland and the same situation.
Same situation here. German device. No 13.1 available. All the VPN that in the past offered immediate update don't work anymore. Has someone contacted the service support?
You can try to download manually from Telegram Group and then copy it to your phone and update from there. This is the TG Channel: https://t.me/oppoitaly
Well people have the freedom to express their views, experiences and compare to other manufacturers.I find it really amazing how much one or the other complains and complains as if their life depends on this update. Constructive criticism makes sense, but switching this talk to another manufacturer is annoying. Just do it and keep quiet because nobody wants to know.