RCS Tips for ROG Phone 2 (or other dual-Sims)
RCS will work if your carrier supports it. If Carrier is yet to support it, follow this guide. (Might have to downgrade Messages app to force RCS enable)
To downgrade uninstall all updates for Android Messages on Google Play Store and use the APKmirror link to get the Android Messages Beta with the RCS enable flags.
Latest version of Android Messages have taken off the RCS flags enable as it's now Carrier-sided enabled (automatic if Carrier supports RCS)
Once used the guide to force enable RCS, then can fully update Android Messages from Play Store to the latest update.
RCS will only work if set all on SIM 1 Only. Was unable to get it working with SIM 2.
If set incorrectly or use SIM 2 for data RCS will be disabled.
This will appear if you set anything else to SIM 2. If set everything back to SIM 1, no need to reactivate RCS again as it fixes itself.