Zoom Web SDK doesn’t support gallery view in Safari, Chrome and Firefox by default.
Gallery view is where multiple participants of a meeting are visible at the same time.
The reason is that SharedArrayBuffer isn’t available in browsers by default.
Safari doesn’t support it right now.
Chrome enables it after achieving Cross-Origin Isolation on the website or by opting into a Chrome Origin Trial(which one?)
Firefox enables it only after achieving Cross-Origin Isolation.
Cross-Origin Isolation is pretty difficult to achieve practically. It requires you to have Cross-Origin-Embedder-Policy(COEP) and Cross-Origin-Opener-Policy(COOP) headers on the main document.
You can’t avoid it on the main document by having the zoom video portion of your website in an iframe because it requires that iframe also has to be in Cross-Origin Isolation.