For Gallery View (mobile app) you need 3 or more participants in the meeting (only 2 participants required for iPad). To displaying up to 49 thumbnails per page in Gallery View:
Zoom desktop client for Windows or macOS, version 5.2.0 or higher
The Maximum participants displayed per screen in Gallery View is set to 49 participants in the desktop client video settings Note: If your computer does not meet the CPU requirements, this option is unavailable.
Please re-read my message. I am complaining about the lack of 7x7 Gallery view in the Linux client. As you can see in the attached image, it was promised by another moderator about a year ago.