I encountered a similar issue when I first started using Tailscale. My fix is simple: disable IPv4 inside Tailscale. Just use the v6 ULA address that begins with fd7a exclusively. This works even if your ISP doesn't support IPv6: the inner IPv6 packets can be encapsulated inside v4 packets. There's unfortunately no GUI to do this; you'll have to change the Tailscale ACL to disable IPv4.
> Just use the v6 ULA address that begins with fd7a exclusively.
perfect, this is exactly what I desired
(I'm having an increasingly high number of sad v4 only LAN devices and planned to move to a v4 block that sits way too close to the one Tailscale uses.)
> There's unfortunately no GUI to do this; you'll have to change the Tailscale ACL to disable IPv4.