Let’s get back to work With another second hand Avicii, in poorer condition and also bought cheaper : it’s perfect for trying, no fear of loosing !
But let’s try to do things properly :
Current OS version : OxygenOS AC2003_11_F.12
downloadable version : OxygenOS AC2003_11_F.14
Both are Android 12, should be OK
Make sure that you can send and receive SMS and place and receive calls (also via WiFi and LTE, if available), otherwise it will not work on /e/OS as well. Additionally, some devices require that VoLTE/VoWiFi be utilized once on stock to provision IMS.
I’ve been checking with the help of this ressource Article : How to Check for Working VoLTE Calling on Android | Medium
My result is that with my data sim card (French carrier FREE), the VoLTE is enabled, calls and text are working.
I’m going to try to install the e-3.2-a14-community version following this advice.
Unlocking the bootloader was straight forward.
I’m following the installation guide on a Linux PC.
All four points are straightforward, just waiting for the script to end his job …
And BOOM, here you are with a clean logo :
It’s a total success. 
VoWIFI is on
Downloading and installing 3.3 was quick and smooth !
Now let’s test a bit more !