Add layer-2 support matrix to platforms overview

docs/platforms.md

@@ -308,9 +308,14 @@ These devices support additional control-plane protocols or BGP address families
 **Notes:**
 * FRHP = First-Hop Redundancy Protocol (anycast gateway or VRRP)
 
-```{tip}
-See [integration test results](https://release.netlab.tools/) for more details.
-```
+(platform-layer-2-support)=
+The layer-2 control plane [configuration modules](module-reference.md) are supported on these devices[^NSM]:
+
+| Operating system      | [Spanning<br>Tree Protocol](module/stp.md) | [Link Aggregation<br>Groups](module/lag.md) |
+| --------------------- |:--:|:--:|
+| Arista EOS            | ✅ | ✅ |
+| Cumulus Linux         | ✅ | ✅ |
+| FRR                   | ✅ | ✅ |
 
 (platform-dataplane-support)=
 The data plane [configuration modules](module-reference.md) are supported on these devices[^NSM]:
@@ -353,6 +358,10 @@ Network services [configuration modules](module-reference.md) are also supported
 | --------------------- | :--: | :--: |
 | dnsmasq               | ✅   |  ✅  |
 
+```{tip}
+See [integration test results](https://release.netlab.tools/) for more details.
+```
+
 ## IPv6 Support
 
 Core *netlab* functionality and all multi-protocol routing protocol configuration modules fully support IPv6. OSPFv3 is implemented only on some platforms.