The TV I have right now can have multiple apps open. But that's the problem. In order to actually close an app that you're not using anymore, you have to do a full factory reset. Otherwise, it just keeps them running in the background until it literally has no more resources for anything at all to run.
Also: the factory reset is done by just holding the power button on the remote while the TV is on until the TV turns off and turns back on again. So you can accidentally do it really fucking easily π¬