You don’t have to self host it if you scroll down there is a list of public instances: https://rss-bridge.github.io/rss-bridge/General/Public_Hosts.html
Reason to self host, some websites don’t like rss bridge because it’s a kind of adblock from their point of view, and they actively block the ip addresses of these instances. If you selfhost it, you can use these sites, because a single user instance won’t generate as much traffic than 1000 users, so they won’t notice your instance
It’s mostly just nginx with a webui. You can even see the nginx config files if you bash into the container. It has the same bugs as upstream nginx. Do not expose the management port to the internet.
Plus compared to normal nginx, it’s harder to misconfigure it. Most of my services are just the default config, so I can’t mess it up accidentally.
About lockouts: Once also happened me, but that was just a messed up update, next update fixed itself. If you lock yourself out you can usually edit the db directly, it defaults to sqlite, but I used it with mariadb.