International roaming / India - has issues

I just landed in India a week ago and have been experiencing the same problems described by others here.

Phone shows LTE/4G full bars, and “Connected” in network status, but there is an exclamation point over the indicator icon, and all apps claim no internet available.

However, while trying different apps, I opened my work VPN (Cisco) and it gave a more detailed error message than just “no internet”, it said “DNS name lookup failed”.

Unfortunately, I did not have a terminal/ping utility on my phone, but using hotspot I was able to connect my laptop and behold, there was internet, but no name resolution
ping/nslookup google.com error
ping 8.8.8.8 worked fine

With that info, I changed the settings on my laptop to use google’s dns server (8.8.8.8) and had internet working at that point, albeit just via hotspot.

I could not see a way to force use of a specific DNS server on my phone (Pixel, android 12) for mobile data, just in manual wifi settings.
The private DNS feature only accepts a hostname, not an IP address, and so that too fails, since it can’t look up the new server to switch to in the first place… a bit of a silly limitation, I think.

Before India, I had been in Japan and Singapore, and had no issues with roaming at all.
So it seems that T-mobile’s own roaming data settings may have a DNS server that is often blocked within India for some reason.

Hopefully this helps some of you too, and maybe T-mobile can help fix this soon.