Huh ... just enabled DNS64 and DHCP option 108 on my OPNsense to see if my phones would enable their CLAT, guessing that I would need to do more work, but it just works™️.
The iPhone reports 192.0.0.3 as it's IPv4 and 192.0.0.1 as gateway, and the Android doesn't show any IPv4 (but 255.0.0.0 as next hop in traceroute?).
Either way, that's another two IPv6-only devices, I'm actually making progress. 😁