My partner has the Samsung Galaxy S10 on TELUS have had RCS chat features enabled.
I had a Samsung Galaxy S10 on Freedom Mobile and had RCS chat features enabled.
I switched to TELUS and brought my phone over / BYOD plan and can see RCS, in Google Messages, however the chat options is now completely removed from my message settings.
All 4 phones in my family were not purchased from Telus and RCS/Chat works on all of them.
The issue may be in the Messages app itself.
Specifically try the section:
It's not exactly as @Syaoran says.
I have 4 BYOD devices and 3 are blocked from VoLTE and WiFi calling but the other one isn't because it's a model that Telus also carries. So it's not a problem with BYOD per se, it's whether the model is/was carried by TELUS. Regardless, it's not a good situation. ☹️