There are many, many non-RGB and even non-backlit keyboards. Where are you looking?

Try mechanicalkeyboards.com

Here is a basic mech kb with no added frills.
https://mechanicalkeyboards.com/products/ducky-origin-black

Both of my own keyboards have the ability to disable the backlights—which is ideal, imo, so I can change my mind later.

Just turn it off? Or keep it as a backlight, set it to one solid color you like with brightness turned down to be subtle but useful.

You don't need to keep it on rgb puke.

Snark aside, pick a keyboard you like for the size/feel/features and find out if its a software nightmare (razer) or not before worrying about rgb (just make sure rgb can be configured).

Das keyboard? Keychron?

Then look for mechanical keyboards instead of gaming keyboards.

Go with the originals. Cherry, das keyboard, unicomp. Even Logitech has backlit but non-rgb lights.

Personally I'm using a Filco Majestouch.

I've never really understood why people specifically avoid buying products with RGB lighting. You can usually just set it to a color you like, or simply turn them off. Instead people don't buy the thing they want because of the "obnoxious RGB". Imo it's like not wanting to buy a nice speaker because when you tried it at the store the volume was too high or you didn't like the sample track it played.

You can usually shut off the rgb lighting all together.

Simple solution: turn off rgb. Usually can be done throigh software or theres a dedictaed fn key combination for it

Or you can go down the mech keeb rabbithole and start collecting nice boards

From what I have experienced the obnoxious RGB lighting is just a settings option. They usually come with a few different types of settings. On my system, I just turn it so it blinks white after I push the button. Makes it nice to glance down and see if I hit the right key sometimes. Otherwise I never use the flashy colors or stuff except to show off to someone who hasnt seen it.

Keychron makes some. I've had two of their keyboards and love both of them.

https://www.daskeyboard.com/

Das keyboard - excellent for years and years.

You could just turn it off? Mine can make an animated rainbow, sure, but I can also just set it to mono-color for some backlight or altogether off.
Given that it cost me about 300RMB, the savings for no RGB were negligible.

You can absolutely get non-RGB mechanical keyboards, but depending on if you mean completely non-backlit keyboards or single color backlit keyboards determines how hard it is to find. If you want non-backlit, its easy, you see them all over the place. If you want single color, your choice is highly limited. mechanicalkeyboards.com has some from Vortex, Varmilo, and KBParadise.

You can just disable the lights?

The 8-bitdo keyboards are pretty solid choices without RGB, off the top of my head.

Ducky makes fantastic keyboards and some have no lights. For the ones with lights, you can turn them off.

I'm using Logitech MX Mechanical Mini. It has nice subtle lavender white backlight. Other notable thing about it is, it's wireless and comes back after inactivity in fractions of second. Something many wireless mechanical keyboards struggle with.

I have a nice das for sale. You can't have my IBM model m though.

look around ebay for a Model M keyboard

Ducky Origin

https://www.daskeyboard.com/daskeyboard-4-ultimate/

Build your own how you like it.
You can almost choose like Legos.

You need to leave away the firstname "Gaming" from your search terms.

I am very late to the party but a friend gave me one of these. Better than any keyboard I have ever had and I'm an old bastard.

https://mistelkeyboard.com/products/aff922daf90083d4382a8e6583885571

WASD Keyboards

Almost all RGB keyboards have a switch to turn off the lighting since some people have their computers in their bedrooms.

Did Das Keyboard go RGB? That’s a (pricey) but great keyboard.

E: just had a quick look. Still expensive, backlit but not RGB, full keyboard. We’ve had one for a decade.

I use a Cooler Master Masterkeys Pro M white LED board with MX Blue switches. It's nominally a gaming board but it's very subtle, the "It's a gaming product so it has to look like Gigatron's left knee cap" is held to a minimum. I mainly use the backlights in the "all keys lit" mode at its dimmest brightness or turned off.

The Logitech K845 only has a white backlight. It's a really clean, professional looking mechanical.

Kinesis makes outstanding keyboards with no RGB. Keychron makes good keyboards that you can disable the RGB on.

I love the WASD Code it's just built like a workhorse. Their newer models have backlighting but it's all white, the only thing you can RGB is the 3 indicator LEDs (caps lock etc...) which are very discrete and personalizing them is entirely optional. No software, everything is done & stored on-board. They're pricy but usually they'll have some banger black friday or holiday sales.

Filco is a typist's professional keyboard.

If you really want the retro experience, you can get a modern USB version of the original IBM Model M keyboard from Unicomp (https://pckeyboard.com). I believe these are made on the same equipment that made the Model M back in the day. Buckling spring keys, metal frame, huge, heavy, and loud. Lots of configuration options and the only lights on them are the (admittedly annoyingly bright blue) lock status LEDs. I've used an original Model M and own one of these. They're amazing.

HHKB could be an option or not i use a laptop's keyboard as a main.

Akko has good ones. They are relatively cheap, but expect to spend ~90 euros on a full sized 110 key keyboard. I like akko cos they genuinely look good, no need for RGB.

TL;DR: Check out the KeyChron K3 V2 Non-Backlight edition. Decent quality, inexpensive, no lights, and no knowledge required.

ZSA make good stuff, sell it at reasonable prices, provide incredible support, and give a shit about artists/humans/the world. Any time mechanical keyboards are mentioned I feel compelled to inject their name into the conversation. I've owned a Moonlander for a while now and I have nothing but good things to say about it. I'd recommend the ZSA Voyager for someone checking out not shitty keyboards for the first time.

With that out of the way: it's tough to find a lightless mech keyboard these days because backlights make sense and, so long as you're putting lights behind keycaps, you might as well use full color range LEDs and let the user set a low brightness white color or turn them off if they don't care for it. Some companies make non-backlight versions (KeyChron's K series for instance) but they're a rarity. Why produce and stock inventory that's not moving?

I recommend doing some research on how mechanical keyboards are built (watch a 10 minute video on the internet) and then using RTINGS' keyboard table for some comparison shopping. You're looking for a well rated keyboard with hot swappable PCBs designed to accommodate south-facing LEDs (they point down - less bright). One of the advantages of going mechanical is customization. Don't want the LEDs at all? Remove them from your build. Even without PCB hot swapping: no one will stop you desoldering LEDs from your keyboard.

Building out something like a Gem80 from NuPhy or a 60HE from Wooting will net you a high quality mechanical keyboard that won't get in your way but is customizable enough for you to avoid RGB-induced eye sores.

I'd be happy with a keyboard deeper than the apparent 1mm the junk is going with.

As a bonus, one that's easier to vacuum for cat hair and similar detritus.

As a second bonus, one I can frustratingly pound when fingers/coding are betraying me. I will never manage that anger.