There are just very few players, unfortunately.

The missions, worlds and defense scenarios can all be played single player and should offer some amount of fun. It is probably best to start with the missions.

Best is to ask in the chat (and wait five minutes to see if someone answers). It's mostly played by Germans in the central European evening hours.

In addition to what Maikel and Sven2 said, it's not possible to host a network game with OpenClonk 7.0 (which most players who just discovered the game have) without having to forward the ports for OpenClonk, at least when hosting a network game in the internet (LAN Multiplayer also works without port forwarding). In the next release (and also in the Snapshots/Nightly Builds which we also play most of the time) this is no longer required (but still possible).