Hydraglass
I did some more research. Actually it’s more like a “whitelist” approach. Bell is a bit sneaky, by only listing ancient models, most of which are already in the landfill. Go to https://www.bell.ca/Mobility/VoLTE and check the “Manufacturer” dropdown. Bell says “TCL 10L, TCL 10 Pro, TCL 20S, TCL 20 Pro 5G, TCL 30 5G, TCL 30 XE 5G, TCL 303”
Meanwhile VirginPlus (my carrier) https://www.virginplus.ca/en/support/voice-and-video-over-LTE.html?province=ON&geoResult=ON lists TCL supported models as… “10 Pro and all newer models”. That sounds better.
Telus meanwhile https://www.telus.com/en/support/article/how-to-use-volte#check-if-your-phone-is-supported has a webpage to enter your IMEI to check if it’s whitelisted.
Years ago I heard that it was a major scam. In extreme cases, carriers would support VOLTE on a specific model if you bought it from them, but not on the exact same model if bought from a 3rd-party store.