Not specifically RO, but even better IMO: https://www.megahomedistiller.com/

Also, it's Made in Taiwan, so not supporting China.

I've been using this one for over ten years and it's amazing. Don't need to buy any filters at all, it's very simple and has just one button. Distilling is supposed to be even better than RO, too.

I've been drinking mainly distilled water the whole time and I'm totally fine. The stuff about it being bad for you is nonsense.

I recently got a waterdrop brand RO filter, which I think will help reduce scale a lot in my espresso machine and probably make descaling faster / easier. I also love basically having no scale build up in my humidifier. My TDS goes from about 100 to 3 or 4 according to the readout on the faucet and my handheld meter. I'm biased though because they accidentally refunded me so I basically got it for free.

I got a "refurbished" G3P800 which looked identical to new and was significantly cheaper than MSRP, so I would check out what they have refurbished on their site or sold through their official store on eBay. They're also on Amazon I'm sure, but I avoid Amazon.

If you choose their cheaper models like the G2 and get a refurbished one they go pretty cheap like just under $200

The RO system is dependent on the membrane. Theres a level of standardization for membranes and pre-filters. This is an example: https://www.freshwatersystems.com/products/axeon-5-stage-ro-system-50-75-gpd Conversely, there’s a lot of branded systems that require special format filters and membranes (https://www.premierh2o.com/ro-pure-plus-voc-system), which can naturally only be sourced from the manufacturer. A good 4-stage system can be sourced for about $200 give or take.

RO was developed to desalinate water. Therefore, if you use a salt-based ion exchange water softener (the standard water softener) and then run that through an RO, it’ll be a pretty straightforward process. The more pressure you can provide up front (within the specs of the system), the more efficient the system will be. (Actually, it’s the pressure differential that really makes a difference, so if you’re pulling out one cup at a time, it’s less efficient than pulling out a litre). If your water is very hard, there will be more brine produced. There are ways to minimize that waste (effectively by injecting it into the hot water supply), if that’s important to you.

A distiller will have the same problems any boiler will have.

I’ve got a softener and a RO. It comes in between 450 and 550ppm and leaves around 30-70ppm. You typically want to see a >90% reduction; less than that and the membrane needs replacing or you may have pressure issues.

I use a 7 stage 3M set up. No idea whether this is affordable or not in your region. Here in SE Asia it was a reasonable price.