Using multiple phones as secondary monitors

[Lord Athetos]

So i've been using for a few months an app called splashtop to use an old ipad mini as an extra monitor for my pc and it works really well, aside from the latency penalty. I've been running out of screen space recently and thought of using a few old phones as extra monitors just like the ipad. However, splashtop only supports using a single device. I looked for more apps that can do similar things and found one called spacedesk, that advertises to do the same thing, but over the network. But when i try to connect it gives an error message saying its not compatible with splashtop. I've looked up in their formus and doesnt seem to be a solution. Does anyone know if this is an artifical limitation for competence reasons of there is some sort of driver that all these types of apps use that makes impossible to use more than one of them? Also is there some other app or other way i could connect more than one device as extra monitors? thanks in advance.