But if you meant the thumb keys should angle down, then I think your only option is to design it yourself with the help of one of the online tools for Dactyl type keyboards.
I am not convinced those are a good ergonomic design however. The thumbs are much stronger for a sideways movement. Like playing the bass guitar.
I don't know of any board that cover 100% of your requirements. I've never looked much into the 34 keys keyboards.
The Piantor is close, but it's wired and 36 keys.
The Totem is 38 keys and adds splay. Might be worth considering though. Here's mine:
You didn't explain how you have your Colemak layout setup but I think I understand the problem. I just tried adding Greek to my computer (Corne keyboard, Colemak DH) and it worked as expected.
Can I suggest you try this:
This way, the computer doesn't even know that you are using Colemak. And it works with all (or most of) the languages!
Miryoku is worth looking at for layout ideas. But using it as-is of a non starter for me.
I'm still slowly making changes to my layout. It has some features that you say you don't like in your blog (numpad on the left) but it works for me.
I thought I needed the aggressive stagger... until I tried it.
I'm in Europe so the shipping to the US would be expensive. Anyway I'm not sure I want to entirely give up on it.
It is the wireless ZMK version, hotswappable switches, resin printed case. It is very nice.
Thanks. I'm used to my own config. https://github.com/y-muller/zmk-config-public I have the missing switches on the keys I use the least, but on some layers I do need them.
A lot of combos, basically.
There is an example of config in the keyboard's repo. https://github.com/kilipan/teenspirit
The repo has never been updated and the file is missing. There is the "default" keymap that doesn't use the dlip.h file; you could try it. If it works, you could build your own keymap on top of it. Another option would be to look for other users' config.