Hello to everyone! As promised more than a month ago, I'm here with a brief update on the results. The hat has been a complete disappointment unfortunately. It seems to be a very old stock (the production date printed on the PCB is back to 2016 and the board is scattered with oxidation signs almost everywhere, especially on the connectors) and it doesn't work: it just emits a clicking noise, nothing else. I've been unfortunate but it could easily happen given that it seems these hats are no longer being produced.
The IR relay has been a success instead. I've paired it with two separate 5V PSUs (a 2A one and another with just 400mA output, the former controlled by the relay feeds power to the RPi Zero, the latter is always powered and feeds the relay) and bought a 3 in 1 learning remote too (by which I control the RPi, the TV and the soundbar connected to it). With just one remote I control everything I need including turning the RPi on and off without the need for plugging and unplugging anymore. Here is the current arrangement:
The cost for all the needed parts has been ridicolous ($2.31 for the 2A PSU, $0.93 for the 400mA PSU, $2.99 for the relay, $2.84 for the remote, $1.94 for TEN IR receivers so I've nine of them still left. $11.01 overall if we don't consider the cables and the connectors that I already had and just the need for some soldering work, easy even for me and I'm not that good with soldering!) and it becomes even more ridicolous if we consider that there isn't any need for a MicroUSB cable and an USB PSU anymore, not to mention the convenience given by the 3 in 1 remote.
Given their very cheap price, I wasn't confident about that (in spite of the fact the seller has a very good feedback) but the PSUs are reliable, well made and they remain cool, always a good sign. No problems at all till now and I've both a WiFi card and a DVB-T2 tuner connected to my RPi.
It's clear it's just a quick and dirty approach, just to get a proof of concept. Now I plan to put everything inside a neat enclosure and find a way to get rid of the second IR receiver using just the one already present on the relay board. By now, in spite of the fact I've already soldered the connectors even on the IR receiver on the relay PCB, I've chosen to use a second one to use a single ground otherwise I had been forced to connect the RPi to two grounds coming from different circuits and I don't like that approach, apart from the fact that the approach had required one more cable, one more connector on the GPIO and another bit of soldering work.
What I'm looking forward more than anything else is finding a way to put everything on the same base with more effective, safe and solid connections. I've thought about a breadboard but this isn't exactly what I'm looking for... I don't even know if anything like what I'm thinking about does actually exist... I'm thinking about something like a multilayer PCB but that's too overkill and too space consuming to put everything inside an enclosure so I'm looking for something simpler (if it does exist and it doesn't, at least to my knowledge).
A nice day to everyone!