Do you actually use dhcpcd as DHCP client? DietPi by default uses isc-dhcp-client/dhclient. Check the network logs: journalctl -u ifup@eth0 or if you use WiFi: journalctl -u ifup@wlan0
You tried to install the dhcpcd5 package from Bookworm “backports”. Was this intentional?
If you did not intentionally install dhcpcd and either no DHCP client is used (static IP), or the ISC one dhclient, purge dhcpcd:
apt autopurge dhcpcd5 dhcpcd
If you intentionally use dhcpcd, first of all purge the transitional dummy package dhcpcd5. The real package is called dhcpcd since Bookworm:
apt-mark manual dhcpcd
apt autopurge dhcpcd5
If you intentionally tried to install the backports version, do this for the real package now:
Then this seems to be a very old instance, isn’t it? Pi-hole removed its dhcpcd dependency several years ago . But makes sense, then you can safely purge both packages. Yes, it won’t interrupt or tangent Pi-hole in any way.
To be true, I never faced a use case where it was necessary to set a static IPv6 address at the host itself:
Every network adapter has a static MAC address based LLA (Link-Local Address).
For Internet access, every adapter gets a GUA (Global Unicast Address). But this must match the global prefix of the router, which is done automatically via SLAAC.
There are ULA’s (Unique Local Address), but it is generally recommended to not enable them, unless really required. Similarly it makes sense to let the router assign these, to assure a shared prefix is used, no conflicts etc. This is also done automatically via SLAAC, if the router has ULA’s enabled.
Basically IPv6 is all about very light/fast SLAAC auto-configuration, and any manual IPv6 address assignment as well as DHCPv6 are needed for edge cases only.
And of course, for access within your LAN, I see no reason to (explicitly) use IPv6 at all. If your router does not promote local hostnames, you can use the anyway assigned static IPv4 addresses instead.
. But makes sense, then you can safely purge both packages. Yes, it won’t interrupt or tangent Pi-hole in any way.