[steve_rambo]

iptables has been with us for more than 20 years and is only now being replaced (pretty slowly I might add). The old rules are still supported through iptables-nft, you can just import them and forget nft exists.

Distributions I prefer have never used NetworkManager and haven't changed network configuration in a long time. RHEL and its rebuilds have used NM for what feels like an eternity. Ubuntu is the odd one out here with its constant churn, afaik.

Same with firewall wrappers like ufw and firewalld. Either your distribution uses one and you just use whatever has been chosen for you, or it doesn't and you go with nftables (or iptables-nft if you prefer).

This is all only really a problem if your organization uses a bunch of distributions instead of standardizing on one, but then you probably have a lot more other serious problems than learning how to configure your firewall...

As a counterpoint, I evaluated FreeBSD for a project about a year ago and was really put off by its primitive service management (compared to systemd which I know pretty well and use its features extensively, they really do help in your daily work), and the three firewalls which all seem to be approximately equally supported and you never really know where to put your time. (Unfortunately, I had to pass the OS for other reasons which have no relation to its technical merit.)