I have a small electric cabinet where most of my ethernet ports to the house end up. Just one cable go under the stairs to the actual OpenWRT router. I want to be able to use vlans so was looking for a small managed switch that has PoE. For some mysterious reason (LLM cough) I ended up purchasing a Mikrotik Hex S. This is more of a router than a switch though. I was pleasantly surprised it has OpenWRT support. If it had more internal storage I'd consider just replacing my current OpenWRT router with it, but that's out of the question because of the internal storage limitation.
Just wanted to hear some opinions: Bad idea to flash OpenWRT on the Hex S and just use it as a small PoE vlan switch?
I had a look at the specs: There are two versions, the original hEX S from 2018 and the new version from 2025. AFAICT, only the old version from 2018 is supported by OpenWrt.
Be aware that the PoE out port is passive only (on both models) while PoE in is also af/at compliant.
Check out this page first if you decide to flash OpenWrt on any Mikrotik device
I would say Mikrotik RouterOS is a very capable networking OS on its own. It has many nice network traffic monitoring capabilities out of the box (using Winbox software). So if you're merely using it as Layer-3 switch, I would say sticking with RouterOS is OK.
PS: Hex S has 1 port PoE-in and 1-port PoE-out only. Not a traditional 4-port or 8-port PoE switch.