My experience is that AT&T fiber for residential use does allow servers and does not block ports. I used to have Verizon FiOS which, also, did not block ports, but that was a business account and so under different rules. Spectrum and Optimum Online business accounts also didn’t block, but I paid an extra $10/month for a static IP back then as well.
It might be the router that is blocking. Most routers these days block port 80 by default. This might be the router built into your cable modem as well.