Here is an updated tutorial for getting RCS on your Android phone.

Edit: It looks like some ACS servers are using a different OTP pattern. If you have trouble, try the pattern listed at the bottom.

Credits:

u/LinkofHyrule - Helped me figure out how to get the original trick working on all Android phones, created list of official ACS URLs

u/NashRadical - Created original tutorial here

Requirements:

1. Latest version of Android Messages

2. Latest version of Activity Launcher

Steps

1. Open Activity Launcher

2. Look for 'Messages’ with a blue icon.

3. Tap 'Messages' and tap 'Set RCS Flags' (com.google.android.apps.messaging.ui.appsettings.rcs.overrides.OverrideFlagsActivity).

4. Select 'ACS Url' and input your ACS URL (find below).

5. Select OTP Pattern, and in the menu tap

'Your\sMessenger\sverification\scode\sis\sG-(\d{6}).'

6. Clear data for 'Carrier Services' (if installed) and force close Messages.

7. Switch back to Android Messages and check under "Chat Features"

8. Follow setup in Android Messages. This can take a few minutes. If you do not see Chat features enabled, force close Messages and repeat these steps.

ACS URLs

Google Fi (US)

http://rcs-pfi-production-acs.pfi.jibecloud.net/

Verizon (US)

http://acs-vzw.jibe.google.com

T-Mobile (US)

https://rcs-acs-tmobile-us.jibe.google.com

Sprint (US)

http://config.rcs.mnc120.mcc310.pub.3gpnetwork.org

US Cellular (US)

http://acs-uscc.jibe.google.com/

Straight Talk/Total Wireless/TracFone/Net10 (US)

http://config.rcs.tracfone.com

Freedom Mobile (CA)

https://acs-ft-fre-ca.jibe.google.com/

Telus/Koodo (CA)

https://acs-ft-tel-ca.jibe.google.com/

Rogers (CA)

http://config.rcs.mnc720.mcc302.pub.3gppnetwork.org/

Three (UK)

http://rcs-acs-hutch-three-uk.jibe.google.com/

Sky (UK)

http://rcs-acs-sky-uk.jibe.google.com/

If your carrier is not listed, use:^*

http://rcs-acs-prod-us.sandbox.google.com/

^* Google will be migrating those on the Sandbox to the correct servers once the RCS rollout has been completed.

Links

My original post

Original tutorial

Official RCS URLs

Alternate OTP Pattern

'Google\sis\sverifying\syour\snumber\sfor\sChat\sfeatures\s([A-Za-z0-9]{8})'