Note that the Flatpak uses a different path to servers.txt

docs/MULTIPLAYER.md

@@ -5,7 +5,7 @@ MCPI-Reborn supports two ways to play multiplayer.
 This is also supported by vanilla MCPI. Just load a world in MCPI and other devices on the network can join.
 
 ## External Servers
-Unlike vanilla MCPI, MCPI-Reborn allows you to natively join a server outside of the local network. Just modify ``~/.minecraft-pi/servers.txt`` and it should show up in MCPI's server list.
+Unlike vanilla MCPI, MCPI-Reborn allows you to natively join a server outside of the local network. Just modify ``~/.minecraft-pi/servers.txt`` (or ``~/.var/app/com.thebrokenrail.MCPIReborn/.minecraft-pi/servers.txt`` if you are using the Flatpak) and it should show up in MCPI's server list.
 
 ### Example ``~/.minecraft-pi/servers.txt``
 ```