Apparently there's not as much evidence as you'd think that ergonomic keyboards make a difference for wrist pain. I used to think I could only use an ergonomic one, but I've been I've been using a brown switch CODE keyboard for almost 3 years now and it's been no better or worse than my old ergonomic keyboards. As long as I don't overdo it, my wrists are fine.
You usually need to figure out what particularly is causing the strain. For instance for some strain types mechanical switches are basically out.
Meanwhile ergo split key keyboards don’t help me as my wrist strain is caused by laziness in my posture. Both standing desks and very resistant keyboards help.
All said I use a code keyboard and don’t have wrist issues. I do have shoulder nerve issues at times (especially when my lifting routine is lax).
Microsoft have a lot of decent ergo keyboard offerings. A friend with wrecked wrists swears by his Sculpt Ergonomic (within your budget and stocked by many physical stores so you can try it in person), although it acts funny under Linux. I have a Comfort Curve 3000 which is under $20. It's the only curved keyboard in this price range I know of.
Imho ergonomic keyboards are not much better. They are hard to learn and you get confused as soon as you use someone else’s computer, plus they have annoying features like a tiny Esc key. I think overall a gaming / mechanical keyboard helps you type faster and more accurately, which itself leads to less strain. I recently got a logitech g-413 and i m very pleased with how fluently it works , without a lot of noise.
For ergonomics you should consider an upright mouse, in my case it eliminated ulnar nerve pain
Mechanical keyboards require deeper compression and are thus the opposite of what you want. They'll worsen strain.
Have you checked your chair/table height, monitor height, and are you placing both feet on the floor? You might be able to mitigate this without buying things.
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https://codekeyboards.com/