Thanks for all your extensive input in the past, and I think I'm getting closer to a solution.

While the solution of using distilled water with potassium bicarbonate added is pretty neat (and cheap), I would like to avoid the activity of refilling the water reservoir. (Particularly since there really is no low water indicator, my machine just shuts off when it is out - and then the power light blinks to indicate low water...) Hence I'm looking for a reverse osmosis system that also remineralizes the water. My preference is for a small system, that also delivers to DC (amzn is fine). Does anybody have a recommendation for such?

Define small system? The Home Master TMAFC-ERP has been popular, and you need the model with the permate pump if you want to reduce the water usage. Pat commented on them here.

Thanks, BuzzBuzz!
Can't define small, other than smaller being better. This looks like a good system though, and I believe it will fit (even if other things will need new homes.)

The HomeMaster arrived today. The plumb in kit arrives on Thurs.from Chris Coffee. I'll install on Friday and will report.
BTW, the entire kit (Artisan, Full Contact, loaded package) is very nice. Quality components. Good instructions in addition to the install videos on YouTube .

The HomeMaster Artisian R/O is installed and the Linea Mini is plumbed.
Instead of installing under the kitchen sink, I located it in the laundry room next to the kitchen. Much easier to install on a wall at eye level than lying under the kitchen sink.
Install was very easy. Great instructions and tech support answered a question within 2 minutes of calling.
Quality parts. John Guest fittings. The faucet at the sink appears and feels like a quality piece.
'
That all aside, the plumb-in to the Linea Mini was not difficult. I watched the video from Prima Coffee and just followed along.
The R/O system (I ordered the "loaded" version had a factory installed T, shutoff valve and hose for a refrigerator/icemaker hookup. This was to be the Linea Mini connection. Only issue was that, while all of the r/o system tubing is 3/8", standard fridge connections are ¼" .
Easy enough to run over to Home Depot and pick up a John Guest 3/8" T fitting and some 3/8" NSF tubing to replace the refrigerator line.(Also got a JG 3/8" shutoff valve)
The Plumb-in kit from Chris Coffee comes with a JG 3/8" fitting at the end of the braided water hose. First test. No leaks but the pressure was at 10 bar.
Since the case was already off, the pump pressure screw was very accessible. about ⅛ turn while pulling a shot and I was back at 9 bar.
I'm very happy with this setup.
Going to run all water tests tomorrow. LM water test kit, TDS, pH, Hach Hardness test.

Really interested to see your #s.. I have the same RO system and I have only tested pH & TDS so far. My pH is about 7.56 and TDS is around 57 ppm. I do have to change filters as I am getting close to that 1 yr mark soon. Really love this system but never been sure if its causing any corrosion

I hope that everyone remains safe and sound!

I'm interested in this RO system for my Profitec Pro 700 - currently I'm using ZeroWater in conjunction with Dr Pavlis water formula (was using distilled water but I can't buy it nowadays...). I understand that I might need different connections as it's a different machine than the Linea Mini...but I do have a 2-part question:

1. are the added calcium and magnesium minerals the recommended concentration amounts for that 'perfect espresso'? Also, what exactly are the ppm Ca & Mg concentrations that this system adds? The Amazon description doesn't seem to mention it...perhaps I missed it.
2. Obviously RO water by itself will corrode the machine internals given its acidic/very low pH level, but is the final water concentrate this system provides safe for espresso machines without the need to descale at some point?

Cheers everyone and Be Well!

from their website: "...restore 30-60 mg/L calcium and magnesium minerals". This is with their Artesian Full Contact model

Thank you for the reply!

So are these concentrates both safe for the machine and provide great tasting espresso?

Thats what I'd like to know ..water tastes good. no issues there. I don't know how it affects my machine tho. pH meter reads 7.56, which I would think is safe? I checked my parents RO system [without remineralization] and I was getting pH readings in mid to high 6es. So, Im thinking its more than just a gimmick