I’m not sure I understand. I have an ergodox moonlander and while it’s true there is no dedicated button for Function keys, that’s what the layers are for. It’s kind of the point of a configurable customizable keyboard.

So for me I have all my special symbols under my left hand while my right hand holds a special key. Takes some getting used to, but once I had practiced the special keys are actually closer than before because they’re all the normal keys. Similarly I have arrow keys under the keys labeled ‘hjkl’ when another key is held. My Function Keys are all accessible with special key and the number keys.

It takes some tweaking and tuning to figure out the layouts you want, but the whole point of a keyboard like this is that you can tune it to be whatever you need it to be. Now, if you don’t like to tinker and just want something out of the box, I get that, but even the default config has function keys, I think. Maybe you just didn’t read about how it works?