@Josephny
Anyway, since you mentioned home assistant, I’ll give you a few hints.
I am - generally speaking - cheap/thrifty, and I cannot resist some things.
I was looking for a single smallish 2.4 GHz access point, and thought that a hap lite (price new some €22+9.99 shipping) would have done nicely for my intended use, when I happened to find an e-bay offer for 4 used hap lites TC for €30 including shipping.
It goes without saying that I have now 3 unused hap lites to play with 
, in the worst case they can be used as “dumb” four port switch.
I made a first (failed for the moment, yet …) attempt as a sort of network “man at work sign” (which is something that would be useful when doing maintenance), JFYI:
http://forum.mikrotik.com/t/is-there-a-simple-way-to-hang-a-virtual-out-of-order-sign/181186/1
Then I thought, what if I could use one of these things as a web/ethernet relay? (yes, single channel, wired, not one of those wifi thingies)
The ones you can find (possibly exception made for a few professional ones that go over $150 or so) are 2 to 8 channels, fairly crappy/no brand and have what it seems to me a very poor interface/web server/command line (and I don’t even want to mention the possible security holes) and ship for €30-€100.
And I have anyway need to find reasons/ways to learn hands on the Mikrotik scripting language.
An el-cheapo photoresistor relay module ships from Aliexpress for (less than) €2 (XH-M131), a “better” one with a delay/timer module (FC-66 or similar) for (less than) €5[1].
One of the fundamentals in using relays is to opto-isolate the command/logic from the load, I can see little better than an actual led+photoresistor as an isolator, and this allows to not open/modify the actual Mikrotik (that could be under warranty).
Of course it is just for fun and sort of half-@§§ed or MacGyverish…
[1] depending on the use the latter may be needed