Some thoughts...
Does a non-android linux system behave correctly through the same NAT gateways?
Particularly with a similar kernel version.
If you have a USB OTG cable and USB ethernet dongle you may be able to get
android to use a wired ethernet connection - excluding any WiFi issues.
(OTG usually works for keyboard and mouse, dunno if ethernet support is there.)
Does you android device work on any other networks?
David
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