VPN is not enough to fool Screen Call. You need to spoof your location, language, use an unlocked App version via sideload and even then chances are slim that it's going to work. Back in the days it was possible to sideload some stuff and activate a couple lines code, but then about a year or so Google changed most of the Call Screen stuff server-side, so you as an enduser can't to ****. They either unlock it for you - or you're out of luck.Thanks for the answers, I double-check I had only one language on the phone. So I guess I only need to wait some times for the Call Screen activation... Would be nice to have a small hack to enable it, but I can wait. I guess it's maybe a random rollup, I don't think it's regional as all french smartphone was packaged to add the USB-C earbuds (french law make mandatory to sell these with a phone as a "hands-free kit" for drivers), but all french doesn't have the feature available at this time.
I also tried to see if it appear after using a VPN (with UK, Germany and US location) and clear cache/force shutdown for the phone app, and still nothing. (I know this was working often with firmware update on my previous OnePlus phone)