Availability Group- multi-subnet Listener

I don't really know Microsoft SQLServer Clustering. Is the listener one of several SQL servers that is acting as a primary node or the like? And if it fails a different SQL server (with another IP) takes over?

It can be a bit complex when it comes to active/passive like situations. If there is a fqdn DNS that will always points to the active system, then it's quite possible that setting the fqdn in LM will have it always monitor the correct device. I would just go ahead and try it.