The last man standing in island settings and round settings device is bit limited and hard to test, the best way is to use player counters (at least 1 per team) and an end game device set to end the round.
Using the functions and events of these devices with each other, lets you customise the behaviour.
Starting out it can be a little tricky to get right with multiple teams, but once you start out it will be worth it.
You can also add different devices to the mix
To provide a better experience, adding another player counter to not start the main last standing counters until a second player joins.
or for playtesting, a button to start the counting.
To deal with multiple teams, using a couple of trackers between the counters and the end game device works. A tracker for each counter, that completes when its counter counts 0, and an additional tracker with a target of number of teams - 1, to count the completed trackers and activate the end game device.
Have a play around with them and post back