Your ROOT_URL in app.ini is https://git.cloudchain.link/ but you are visiting https://dash.bss.nz/open-source-mirrors/overseerr/blame/commit/4a00617fe47064ea50f95a02f29832a419ab13a3/docs/extending-overseerr/fail2ban.md
You should set ROOT_URL correctly, otherwise the web may not work correctly.
You can then add a jail using this filter in `jail.local`. Please see the [Fail2ban documetation](https://www.fail2ban.org/wiki/index.php/MANUAL_0_8#Jails) for details on how to configure the jail.