I would like to share my experience with different devices across this years as a developer and which I find useful or worth.
Specially those who makes our work healthy.

Without further delay here it goes:

Chair: I was looking for an ergonomic chair that adapts well to my body for long time, I finally found one that I tested for three months and my back is happy, ThunderX3 Yama 1. It's a 150€ budget one, you can adapt different parts to you and it feels good in my opinion. For reference, I'm 1,81m (5,9 feet more or less) tall. I think it could not be as useful for a person taller than 6.1 or 6.1 feet.

Keyboard: I adapt easily to a new keyboard but I type fast with low profile ones and I feel less tired with them. I like Huawei laptop keyboards, MacBook ones and for my desktop I get a Logitech G915 wireless. It's a 200€ keyboard but you can go for G815 one which is the same but wired. 5 months testing and I'm loving it.

Monitor: Its inches will depend on the distance from you to the monitor. I've like 27 inches of distance from my head to my 27 inches monitor. I have 3 monitors on my computer, another 27 inch one set vertically at left from the primary screen and another 25" ultra-wide at the top, there are people that prefer a 32 or more ultra-wide instead using 2.

I've tried different panel technologies such as TN, VA and IPS, curved and flat. I definitely prefer curved ones for setting it clockwise rotated (portrait) and flat for primary non-rotated (landscape), and I prefer IPS with low blue light feature and AMD FreeSync, it makes me feel less tired at the end of the day and there's no tearing, which is a common problem on Linux, specially on intel graphics.

Mouse: I didn't tried this supposedly ergonomic mouses that you have to take as a beer bottle (I mean, with you hand rotated like if you gonna play drums) so I can't give my opinion, but i definitely love Mad Catz mouses. I've an old R.A.T. 7 which came with customization pieces to adapt it to your hand. I'm in love with a piece to rest your lil finger and the option to make it heavier or lighter for FPS gaming or work. I think the equivalent model nowadays it's called R.A.T. 8+, check it out.

Headset: Oh boy, I tried loads of them since I found the Corsair Void Pro wireless headset, now I'm with a Void Elite Wireless ones and my GF uses my old Void Pro. I love this headset series for the comfortability. The adaptive foam, the ear pads that lets you hear the ambient sound if you use it at low volume, the fact that the air could pass a little bit through this pads... all together avoid to feel tired and get headache after long sessions in front of my computer.

Computer specs: It will depend on the languages you use and the size of the projects you are in. If you are into heavy computation you will prefer a heavy duty multicore like a 3950X or a threadripper while a reduced stack dev would run OK with a laptop with an intel i5 (fill the range in between).
For me, a 4 core 8 thread CPU is enough for front end (which takes the 90% of my time). I had a R7 1700X which was 8 core 16 thread and recently bought a Ryzen 5 3600X which is 6 core 12 thread and it runs nice for all my purposes.

I also go with 32GB RAM that I never fill (16 must be enough but 8 could be a hell with some Git UI + IDE + project indexed + watch and so).

For a GPU i don't need much for work, but I also play some games and sometimes I play with ROCm so I've a Vega 64 that gives me more power than needed. If you are not interested on AI or gaming, a built-in GPU could do the trick or a cheap AMD card for FreeSync could help. If you have a G-Sync monitor (which is the same as FreeSync but expensive) then go for a Nvidia one, which will let you use tensor flow for example, if you are in machine learning (you can also use tensor flow with an AMD GPU using ROCm platform).

I've also a 14" Huawei laptop with a R5 2500U CPU with vega integrated graphics and 8Gb RAM that lets me code from the sofa without issues but without the power of my desktop.
I coded entire android apps from it and patch some websites too, all OK.

Thanks for sharing