I don't know - the Jibe servers are at Google's end so why they're doing a staged roll-out is beyond me. They do a staged rollout for everything (such as Meet), which defeats the purpose when the world has already moved on (and their staged rollout is still rolling out). Google doesn't have the smartest thinkers all the time. RCS is another example (too little too late).
I don't know if the operators would make an announcement since it doesn't particularly help them, and from what I've read, Google releases these country-wise, not operator-wise, ever since they decided to "ramp up" the rollout (which is still staged, mind you...)
Go to apps > three dots > show system apps > Carrier Services > Clear Data (you may have to tap on a button named "storage", depending on which phone you have).
Go to apps > Messages > Clear Data (you may have to tap on a button named "storage", depending on which phone you have).
You don't add a phone number manually - you usually get the pop up... that's how it was back when the "leak" came out.