For the APC, use nut :)
There is a documentation update pending merging in the official documentation that covers how to do use the Firewall in 4.2.
https://github.com/QubesOS/qubes-doc/blob/86a6f12e2a882dfffb...
https://www.redhat.com/en/blog/using-iptables-nft-hybrid-lin...
For the APC, use nut :)