Hi,You can use pure "iptables" and "iptables-persistent" as a third option. It will be more efficient to learn iptables syntax and use it on any distro than learning syntax of a different wrappers for iptables like ufw and the others.
I'm a long-time Linux user (two and a half decades since Slackware 7.1). I've been using RHEL clones mainly for the last ten years or so, on desktops as well as servers (local and Internet-facing). For firewalling I simply chose the default Firewalld.
I understand under Debian there are different possibilities to handle firewalls. As far as I understand, ufw (Uncomplicated firewall) seems to be the default, though Firewalld seems to be an option.
Any recommendations ?