3.0.2
https://codesandbox.io/s/elegant-silence-k52xk
Go to https://codesandbox.io/s/elegant-silence-k52xk and click the tabs.
The contents of Tabs.vue's slot should change.
The contents of the first tab displays, but never changes.
I have the same code in a vue 2 sandbox and it works as expected. See https://codesandbox.io/s/hungry-hill-lf8xo.
I have looked but cannot find any documented reason why this wouldn't work the same in Vue 3.
You need to add a key to the slot:
<slot :name="activeTab" :key="activeTab"></slot>
Most helpful comment
You need to add a
keyto the slot: