The device list you linked is displaying all end-of-life equipment.
Non-DOCSIS-3 (EOL) Comcast-owned equipment will eventually be replaced sometime in the near future, as a matter of course.
You should be able to go to a service center and swap yours out if you decide to keep renting.
The are only two Comcast approved telephony equipment vendors; Arris, with the most recent model being a TM822G and Ubee, DVM3203B
I would call first, if you intend to purchase a voice eMTA to confirm your area allows customers to do that and to verify the model that you intend to buy is compatible.
Keep in mind that while you will save money in the long run by purchasing your own equipment, consider if you have any service issues, they will invariably point to your equipment as the suspect cause.--
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