So far there have not yet been any 802.11ax cable modems available in the marketplace. It seems that DOCSIS 3.1 modems are mostly provisioned with wave 2 802.11ac capability. While most cable modems are in place for years on end, it seems that industry has been slow to modernize. There are still no DOCSIS 4.0 cable modems at all available.
802.11ax was designed for a mesh topology which can handle everyone with a mobile device connections so that WiFi calling and other services are all operations.
To support 802.11ax will require a quad core processor to handle a larger number of devices. The Intel AX210 is a tri-band WiFi card that can be mounted on a system board. Using a M.2 design would allow end advanced users to modernize when a new standard is released. Linux is the most common operating system and a browser based user interface is standard. Bill of materials is maybe $100 per unit.
The outlook for DOCSIS 4.0 is likely to be available in 2022 or 2023 depending on the rate that fiber is installed into residential neighbourhoods. DOCSIS 4.0 supports 10 gigabit speeds which will require 10GBASE-T ports which will require a much faster processor. DOCSIS has the advantage of ongoing use of the existing coaxial infrastructure.