There is an updated pull request by ahesford against master on the void-packages repository

https://github.com/ahesford/void-packages sshguard
https://github.com/void-linux/void-packages/pull/18477

sshguard: support dynamic firewall config and remove iptables dependency
sshguard uses iptables as an optional firewall backend, but also natively supports the nftables firewall. I removed the explicit iptables dependency from this package and added support for a "conf" file in the service (renamed to "sshguard" from "sshguard-socklog" because it is not inextricably linked to socklog) to allow the firewall and logger service dependencies to be dynamically changed. By default, the service still expects socklog-unix and iptables.

The rename will break /var/service links to the existing "sshguard-socklog", but the post-change behavior seems to make more sense.

A patch file from https://github.com/void-linux/void-packages/pull/18477.patch is attached