2 or more devices?

[ghost]

Eg one phone that works by "monitor" and 2 or more phones that work as "cameras"?

--- Same mechanism of only one, but with a button with the number (perhaps at the top right) which allows to pass to the other or (bottom) a thumbnail of the other

[PanderMusubi]

https://f-droid.org/en/packages/org.avmedia.remotevideocam/ does