Home Internet Port Forwarding working in 2021?

I just got a 4G modem with a hotspot sim.  It worked great at first, but then I figured out that nothing could connect back in.  I've read some of the posts above and it looks like some people have gotten around the problem with VPN.  I understand that the IPv4 addresses are scarce and this is behind an IPv4 NAT, so we never get to see the real IP address.

I was wondering if they could just assign everybody a static IPv6 address.  There is no shortage of those.  I think I could probably work with that.

I got this as a replacement for cable.  So its starting to look like I'll have to call the cable guy up and apologize for all the nasty names I called him.