vanryn So you ask for the APN settings and then don't share them yourself?! SMH
To clarify, it seems this problem is specific to Xfinity mobile and unrelated to DNS or VPN despite OP's assumptions. I'm not familiar with how this is supposed to work, but presumably the carrier should be able to set the APN settings automatically and this is not happening with Xfinity on GOS. Maybe the title could be updated to more accurately represent the problem?
@Sugsolo I saw you in a couple other posts with seemingly the same problem. Try this.
To manually configure APN, go to settings -> Network & Internet -> SIMs (Xfinity Mobile) -> Access Point Names -> plus button in the top right. You are now manually creating an APN configuration. Enter the values shown here: https://www.apnsettings.org/us/xfinity-mobile/
On my old phone, I had the same for all except the following:
APN type: default,supl,dun
APN protocol: IPv4/IPv6
Bearer: HSPA, GPRS, EDGE, eHRPD, UMTS, LTE, HSPAP, HSDPA, HSUPA
MVNO type and MVNO value seemed to populate automatically.
I used the values of my old phone with success, and I'm not sure how significant the differences are between my old phone and the apnsettings.org config. Maybe try the one on apnsettings.org first.