I know they do some hotspot restrictions over there in US.

You should be able to get around it with something like TetherFi: https://github.com/pyamsoft/tetherfi (Android)

It creates a legacy Wi-Fi direct group and runs a proxy server on the phone. You can then connect via the proxy in some programs on your computer (e.g.: Firefox).

You can also run a proxy server in Termux. I use tinyproxy because it's easy to setup.

Both of these will also go over VPN if you have that connected on your phone, as it's basically the app (proxy server) using internet on behalf of your computer.

Alternatively you can also use socat for port forwarding, for example to a public VPN server. Then on the computer you could set up the VPN connection as usual, but replace the IP/Port with those used by your phone locally.

I'm in the US on T-Mobile and have no problem with hotspot. What phone? On a regular plan, not a pre-paid?

Have you tried some basic network tests from the device that is connecting to the hotspot?

Since a hotspot is turning your device into a router, simple things like ping or traceroute can start to tell you some basics of if the configuration is correct.

Also check your connected devices default gateway and make sure it matches your wifi hotspots IP as given to your connecting device.

EDIT: I just checked and there are indeed SOME plans from T-Mobile that don't include support for hotspots. Check your plan to make sure, and then try the workarounds from /u/lukmly013

Some phone carriers prevent people from doing hotspot sharing of their mobile internet.

Your carrier might be one of them doing that.

If your phone is unlocked, you could install a open operating system that doesn't restrict you. Like calyxos, lineage os, or grapheneos