What app? … that is kinda relevant and you should open a Bug that they need to support pipewire portals for screenshare.
Or, as said, use the browser version.
Zoom runs fine in the browser, and it way less invasive. Keep in mind, that “screenshare works” that this app can record everything you do as long as it is running. And if it is a native app (no flatpak) then it can also start how it likes.