@yvaillancourt when I do insist on ipv6 settings that is only to prove a point - it’s not a solution.
I still think the APN setting must be kind of at fault, not the carrier. You could compare between what addresses rmnet_data1 are assigned between v2.5 and v2.6. Searching and comparing your mcc and mnc (for you mnc="370"
) in the apns-conf.xml that is distributed with each /e/OS release if they differ. What is your exact version/build string?