I reinstalled Google Messages (GM) & this time it showed my phone (jio sim) as supporting chat features. I sent a msg to an Asus max pro m1 (jio sim) wth GM it detected destination correctly fr a chat msg. And it went thru as chat msg. So that works.
Next I uninstalled GM and used default Samsung Messages app (SM) to send to the same phone again it detected it incorrectly fr sms only & not chat though its default msg app is GM with correct settings. So sending (source) from another msg app though it supports chat features will NOT deliver it as chat though receipent app is GM. @Sushubh Did the experiment works fine with GM at both ends but not otherwise atleast not with SM as of now with above mentioned phones & jio sim at both ends. Hope this helps others.
When I tried the experiment yesterday with my friend, his phone has airtel sim in slot 1 & jio sim in slot 2. Maybe thats why it didn't work. He found that his phone does not support rcs though both of us use Samsung M31. Also other members have observed that currently GM does not support dual sim functionality yet.
My Samsung A8+ which earlier displayed Chat settings (when Jio sim was in Sim 1) in Samsung Messages app does not show this setting when only Idea Sim is inserted at Sim 1.
It means it only works with Jio sim, and Jio sim should be in Sim 1.
Samsung has started rolling out support for Google's RCS-based Chat features in the Samsung Messages app for some users.
i am quite happy with google's sms app. but this is nice. most people tend to use the sms app that came with their phones. getting them to switch to messages to enable rcs is not always helpful. i hope mi and other chinese players would also add support though seems unlikely. is mi switching to google messages app as default sms app in newer devices? i remember reading something about this.