@rdl85 I was notified by email. Carrier can see what device you use, I guess? I think they only notified affected devices.
My issue turned out to be device specific, not UT related. I use a Oneplus 5T, and the Telus network stopped supporting MMS on many older devices, mine included. Per Public Mobile forums, MMS wouldn't work with Android either on a Oneplus 5T, Iphone 5 and earlier, many other older Android phones.

Freedom Mobile setup:
Freedom has separate APNs for internet and MMS, which my phone seems to need for MMS and internet to function simultaneously.
APNs loaded automatically on UT 20.04, so it all just worked right away. I had to do it manually on my device that still uses UT 16.04. Anyhow, it all works great, with standard lack of proper functionality of Group Messaging.

In case needed:

Internet
APN: internet.freedommobile.ca

MMS
APN: mms.freedommobile.ca
MMSC: http://mms.windmobile.ca
Proxy: 74.115.197.70
Proxy Port: 8080

Note that Freedom uses other networks when outside their own coverage, with free roaming. UT has "Data Roaming" turned off by default. This must be switched on under Settings->Mobile for data to work outside the Freedom network.