Operating system: Debian 10.7 Buster SSHGuard version: 2.3.1-1 Firewall: nftables
When starting SSHGuard via systemd, I would get the following error and notice that the tables/sets/etc. were not being created in nftables:
sshg-fw-nft-sets: Could not initialize firewall
I reviewed the script that was run (/usr/lib/x86_64-linux-gnu/sshg-fw-nft-sets). If you remove the redirection to /dev/null on L20, the firewall initializes correctly and everything works great.