I’ll keep my answer focused on KDE Connect as I no longer use a TWM. You can most definitely use KDE Connect in non-Plasma environments. For non-Plasma (and non-Gnome ^*^ ) environments you can just install the kdeconnectd package. Then, to start the KDE Connect daemon manually, execute /usr/lib/kdeconnectd. You can schedule this to autostart as a systemd unit, or in the config for your TWM (I know in sway/i3 you could start it, I’m assuming it is similar for many other options)
If you use a firewall, you need to open UDP and TCP ports 1714 through 1764. If you use firewalld specifically, there’s an option to enable KDE Connect rather than manually specifying it. This also let’s you have it only work on private networks and not public if you so chose.