I wonder if your carrier can give you a clue about how your IMS registration shows up from their end ?
We see this warning on many install pages, including Install /e/OS on a Google Pixel 7 - “panther”.
Warning: 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.
Did you take this precaution ?