It’s easier than that to proxy non-secure SUPL connections for a test.
Run this on a public server:
./go-tcp-proxy_1.0.2_linux_amd64 -l 0.0.0.0:7276 -r supl.google.com:7276 -h -vv
Now if your phone connects to your server (you need to put your server name or IP into gps.conf
SUPL_HOST setting) you will see the data proxied between phone and Google.
This will show that the device modem is actually connecting the SUPL host and everything should be working.
If the hex output indicates a TLS connection (you will see TLS hello packet data in the hex output) then your phone still tries to use a secure connection so you should disable it using the patcher.