I cannot know from the opening page, what coffee machines the mod is for, but I can see that an STM32 or an arduino nano and some other parts would be needed.
Not really informative, no pictures on the opening page to show something like before/after, to showcase the benefits, etc.
Yet there is a rickroll...
This is not really sympathetic, but yeah, I can see the begging icon (support paying for a professional technical writer)... but this is also really backwards in my opinion. First you should sell the project to me, then ask for donation.
While the engineering contents might be great, the presentation is very low quality, to put it politely.
This is so vaguely written as to seem far more daunting than it probably should, it's unclear how much money or time it would cost me, I don't even know where to start with it. Cool idea, but totally unapproachable to someone without extensive related background.
I'm not sure if I'd recommend it to someone else - and if I was doing it again I'd probably spend a few hundred more (than the gaggia + parts cost) and just buy an off-the-shelf machine with the same feature set.
If you're looking at manual flow control, basically any E61 group machine can be outfitted with a needle valve for flow control, and a bunch of machines come with one installed from the factory, like the Lelit Bianca. There's also machines like the Slayer 1 group and La Marzocco GS/3 MP.
Gagguino is very cool, and if you're just pulling espressos and not too many back to back, it should be plenty of machine. If you're doing more than a couple of milk drinks, or pull lots of shots back to back, or want to connect it to plumbing, it's not as great of a machine. The fact that you started out with a small single boiler with a vibration pump starts to show.
But the recommendation was more for budget purchases. Breville also do a dual boiler with 58mm which is more expensive but if you live in Australia is amazingly good value (often $900AU which is about $600US). If you have more money still get a La Marzocco or whatever :-)
My taste is to avoid fiddly things that need too much skill like heat exchangers etc.
https://www.auberins.com/index.php?main_page=index&cPath=6&s...
Meanwhile, one can also get a temp-controlled kettle, a V60, a years supply of filters, and a hand grinder for ~$80. Skip the temp control and hand grinder and you are down to $30 or less.
It is better than daily takeout, sure..but lets not pretend it is just a randomly affordable purchase for most when brewing non-espresso is far cheaper for good quality. Trust me, I know, I spent the money on mine. Love it, for sure...but is every bit a luxury good.
Now for really affordable (almost-)espresso there's always the blade grinder + moka pot, of course.
(anyway "affordable" is highly subjective ofc so what does it even really matter :))