What is the most valuable data to gather from logs during beta tests?

We have recently done our first ever alpha phase with our new app. We saw that we don't have very useful logs, so my question is what the key is to get useful logs.

Some information: it is an electron app and we currently log everything that our third party shares. We also log the app version and OS information. What else should be useful to be logged?

(deleted original post since title was not correct)