When installing Tailscale using dietpi-software, it sets net.ipv6.conf.all.forwarding=1 in /etc/sysctl.d/dietpi-tailscale.conf, preventing IPv6 address acquisition via RA/SLAAC.
This results in issues with PiHole when it is set up as dual stack DNS server for instance.
The issue can be resolved by creating /etc/network/interfaces.d/eth0-ipv6.conf with the content:
iface eth0 inet6 auto
accept_ra 2
Can the installer be configured to set this automatically when IPv6 is enabled and Tailscale is installed? See also this topic: No IPv6 on DietPi with SLAAC