I got a Galaxy S5 on BT Mobile last year and had a play with tetehring whch worked fine.
I tried again recently several times and cannot get it to work (from Windows 10 and Windows XP PCs).
Computer connects to the phone on WiFi OK.
Phone connects to Internet on 4G OK.
But when I connect to the tethered mobile phone I cannot get the Internet. Been looking around various places and set DNS to 188.8.131.52 / 184.108.40.206 but no difference. Tried ipconfig to flush and renew DNS but still no difference.
If there something obvious that I am overlooking?
Leave the DNS settings on auto.
On one of my phones the procedure has one more step, you must give permission for the connected device to access the internet. So allow 4G and turn on WiFi and connect the computer. Just make sure there is no toggle anywhere where you give permission for the computer access to the internet!
I did initially leave DNS on auto.
I will have another try later.