There are exactly three main things ergonomic keyboards need in order to be correctly ergonomic:
1) Split (so the distance is adjustable for your body, depending on your shoulder width)
2) Two axes of adjustable tilt (sides tented down, far side angled down)
3) Palm rests for when not typing
It's shocking to me how many ergonomic keyboards get the first two wrong -- they're not split, and/or the axes aren't adjustable at all or only one is.
This keyboard is split (yay!) but appears to be adjustable only along one axis (boo).
All three of these are dwarfed by key wells (i.e. do the keys sit in an indentation, or do you have to tilt your wrists upwards?) for me. It's always subjective.
It's actually entirely objective, in terms of the amount of tension you need to hold in the muscles connected to your shoulders, elbows, and wrists. You're looking to maintain a neutral position in all of those, to minimize tension there. There's nothing subjective whatsoever about that, tension is very observable.
Second, I would very much push back on key wells for the general population. Adjustable tilt forwards on a flat keyboard achieves everything you need for neutral wrist position and relaxed fingers, so that you're always typing slightly "downwards". Key wells try to accomplish a weird goal of holding your arms/hands in a fixed position and typing with just your fingers, instead of typing with your whole arm floating in an integrated shoulder-to-fingertip movement. If you have some kind of arm movement problem/disability then concave wells might be the best solution, but for the general population the wells are more awkward to use in the upper rows of keys, increasing the forearm tension which controls the fingers. (As a general rule, tension is usually minimized overall by distributing work across as many muscles as possible that involve longer muscle trains, rather than localizing work in shorter areas. That, for example, is why people say to lift with your back, not with your arms.)
This is why I'm telling you this is subjective, as much as you'd like to reduce it to some "objective" criteria. I broke my wrist a few years ago, and since then typing on anything without key wells is a bad idea.
I've seen too much advice like yours leading to people with some specific problem going "but I'm doing everything correctly, how am I still experiencing problems?!".
Sorry, yes -- if you have a wrist injury that makes perfect sense.
And that's precisely why I wrote that key wells were a bad idea unless you had an injury/disability.
And on the one hand I do want to stress that this is still entirely objective -- it's about actual objective muscle function, it's not subjective opinion. But on the other hand, I can appreciate how frustrating it can be when the advice is geared for people without injury, but presenting it as if it applies to everyone including those with injuries. Sorry if I came across that way. It's just my own frustration with so many quack "ergonomic" products that defend their products which create injuries by suggesting that consumers should just decide for themselves, because the manufacturers are just providing "options".
For me, the most important thing by far is to not have to extend my pinkies to another column. A good thumb cluster and mod-tap implementation dwarf any of what you listed for my needs.
Another obvious thing that few keyboards get right is to use the thumb in opposition to the fingers. Practically that means chords should involve the thumb and another finger. The Kinesis thumb keys aren’t bad for this.
Anyone wanting to design a keyboard or even just remap an existing one should read John Napier’s excellent book Hands[1].
Any recommendations for a keyboard that does everything well?
I have found Microsoft Sculpt to be pretty decent. In particular, it has negative tilt which I think is the most ergonomic option. Build quality is not very good, though. And I would prefer a wired option for a lower latency. Also, I have heard they are no longer produced and they are just selling stocked items. Interestingly, I do not dislike their shallow keyswitches. I find them much less tiring in the long run, and I type much faster.
If my Sculpt dies and I can’t replace it (a useful thing to know is they have a 3 year warranty, in the UK at least, so when a key inevitably fell off my last one I was able to get it replaced for free! I didn’t realise the warranty was this long previously and just bought another), I might try the Logitech K860. Looks nice, though I’d rather not have the num pad.
This Advantage360 looks pretty great but I wonder how easy it will be to ship to the UK, when I last looked into these more bespoke keyboards it was a bit of a hassle and increased the price significantly.
I switched from the sculpt to the Logitech and I'm pretty happy with that choice. It helps that I also have the ergo max trackball and they both run on the same transceiver.
A keyboard tray would offer the additional axis of tilt. But my keyboard tray’s depth does not fit my kinesis advantage2 and I doubt it would fit this. And I bought the largest tray I could find.
1) Split (so the distance is adjustable for your body, depending on your shoulder width)
2) Two axes of adjustable tilt (sides tented down, far side angled down)
3) Palm rests for when not typing
It's shocking to me how many ergonomic keyboards get the first two wrong -- they're not split, and/or the axes aren't adjustable at all or only one is.
This keyboard is split (yay!) but appears to be adjustable only along one axis (boo).