It is hard to estimate what fraction of home users have IPv6 connectivity on a given date. The Google statistics are interesting, because they clearly show weekend peaks in IPv6 access (up to 43% in April 2023), suggesting a quite high level of home and/or mobile IPv6 connectivity.
Some, but not all, devices on the market for home (or small office) use support both IPv6 and IPv4. However, older devices only have IPv4. For this reason, a typical home network today runs a dual stack. Also, a typical network does not include multiple subnets; the only router present is at the same time the subnet router and the CE router. Assuming the ISP supports IPv6, regardless whether it provides native IPv4 or IPv4 as a service, the router provides a dual stack service on the LAN. The LAN itself is typically WiFi, possibly bridged to Ethernet. (Even if the CE router does not support IPv6 at all, link-local IPv6 should work.)
As a result, things are fairly simple. Devices such as PCs and printers can communicate with each other using whatever works -- IPv4, link-local IPv6, or global IPv6. (For example: a Windows 10 PC installed in 2019 communicates with a Canon inkjet printer installed in 2022, using link-local IPv6, needing no manual configuration.) Connections to the Internet will be preferentially established using IPv6 for services that have a AAAA address in the DNS, or IPv4 otherwise. Such connections may be optimized by the Happy Eyeballs technique [RFC8305]. Most home users will remain largely ignorant of all this.
The situation becomes more complicated when various home automation devices are considered, especially if it becomes desirable to split the home network into separate subnets. Such networks need to be essentially self-configuring and self-managing, as do "Internet of Things" networks. These complex topics are out of scope for this book.