Yes. fairmeeting uses the WebRTC standard, which has encryption built in. The start page is of course also encrypted.
Use a name that is not easy to guess, otherwise uninvited guests may turn up in a room such as Yoga or Mama. A warning will be displayed for overly simple room names.
When you are in a room, you can also lock it by setting a password and then pressing Return. Latecomers will then be required to enter the password.
One-to-one conversations typically run peer-to-peer (i.e. not via the server). However, the audio and video stream is always AES-GCM encrypted regardless. If all participants are using a browser that supports insertable streams (Chromium, Chrome, Edge, ...) then E2EE can additionally be enabled in the security settings. This means the conference is fully end-to-end encrypted (for a technical explanation see the forum).