I was able to install Twint (BEKB). I tested it and could send money.
I first tried to install Twint Prepaid, which I was using before switching to GOS, and it wasn't possible: "This app won't work on your device". Also, I couldn't find an official apk from Twint to try to install the prepaid version manually.
Installing Twint BEKB was not straight forward. I first tried the process through "I am using Twint for the first time" --> which didn't work (at validation in the BEKB banking app, the process got somehow killed).
After a few days I gave it another shot: I gave all the rights to the Google Play App in GOS and tried the onboarding process through "I am already using Twint" --> and it worked !
I don't know how the Twint apps for the other banks work, but for BEKB you also need the BEKB app on the phone + have to generate an onboarding code for the new device from you e-banking portal. Onboarding the Twint BEKB app and validating/logging in to the BEKB banking app, worked perfectly in the end.
I'm really happy, as this would have been a show stopper. Now I can switch 100% to GOS.