I've been using a TADA 68 with Opteron brown switches for a couple of weeks now and it's very good.

When I was unboxing it my wife jokingly asked if it comes with a green CRT monitor. The look is unmistakably sourced from the '80s, but why change the design that's perfectly good. She actually likes it now. I was initially skeptical of the plastic base. But the base is just the right weight and it doesn't slide around the desk.

The good:

Great typing feel. Well configured secondary layer accessible via Fn key. I had no need to do a custom layout. The description doesn't tell you that the function keys exist. They are mapped as Fn 1, 2, 3. Not too loud, but I try to reduce keypress velocity when people are sleeping. It feels well manufactured. Great form factor. The keys are spaced out very comfortably , yet not too far apart, and the keyboard takes only a minimal amount of desk space. Very good price for what you get.

The bad:

The mini USB cable jiggles left and right in the connector. But this may be by design to reduce stress on the connector, I don't know. I wish it had a built in USB cable. The configuration web page initially loads in Chinese which is odd for a "U.S. designed" product. Even the manual is printed in reverse. How difficult would have it been to make a separate English language configuration page?
The keyboard has an LED backlight. But it's utterly useless. It doesn't shine through the key caps. The light spills from under the keys. This actually hurts key visibility in low light. I keep mine off.

I initially had a problem where Windows 10 was slow to register the USB keyboard at login screen. The login screen would just hang for twenty seconds or so before the keyboard would become active. I don't think it was keyboard related. The issue went away. Prior to this keyboard I was using a PS2 keyboard so I don't really know if the issue was there all along.

Upon first seeing the simplicity of the TADA68 design I knew I had to have it.
Unfortunately my soldering skills have degraded over the years and I knew it would be a financial risk to try and put one together myself.
So, I was overjoyed when I found a vendor offering the TADA68 ready to go out of the box!
Nothing fancy, just meat and potatoes. Everything you need in a 60% keyboard - nothing you don't.