You will need to speak with Verizon directly, RCS is a carrier based application.
My only recommendation is to continue following up with your carrier as we have no information on carrier specific software or features.
I contacted VZW via chat. Here's what I discovered...
Hope this helps... some. And, I hope we soon get RCS.
The Note9 also no longer supports RCS after the July security update. Tech that I spoke with said that there was no current window to fix the issue. Glad you were able to get a little more information from someone talkative.
@JewellIV That is because Verizon RCS is only proprietary at the moment. Any unlocked unbranded device will not work. You will need to have a branded device. Also since it is proprietary the person receiving your texts must also have a branded device on the Verizon network. Verizon is currently beta testing RCS to be universal but the only obstacle is connecting to the Google jibe