Of course, whoever starts the conference can specify that all participants join without video. This also saves bandwidth. To do so, open the additional settings via the three dots in the menu bar. There you will find the options "Mute all" or "Disable all cameras". This allows all participants to be muted or all videos to be disabled at short notice.
Alternatively, under "More settings" there is a menu item called "Settings", where under the "Moderation" section you can select the option "All participants join muted" or "All participants join without video". This means that participants are muted from the outset or their video is disabled from the start.