Xfinity provides /64 prefixes to their customers. There must be some missing configuration on your router.

I have a 10/10 score.

Yeah they were providing me a /60s worth of /64s via PD when I was using them back in 2015, they were really one of the leaders in v6 to the home.

I’ve used ipv6 on xfinity for years, but I do use my own equipment. Unless there are regional differences it’s important to make sure it is set up right in your router.

You're absolutely right. I'm in the same situation. 10/10 ipv6, but it took a lot of configuration. I'm sure if the parent commenter connected their device directly to their modem via ethernet they'd find they had a functioning ipv6 address. Comcast is terrible for lots of reasons, ipv6 isn't one of them.

exactly what happened. I had ipv6 disabled on my amplifi router, quick switch and its all systems go

oh damn, let me check on my router then

While I generally hate comcast, xfinity has good ipv6 support. It may be an issue with your router configuration.

I have a /60 and it's been working great, had it for some years. Seems like the leader for ISPs in the USA.