Coffee

Unless you are buying your beans from somewhere like Starbucks they should not be that oily that the grinder needs its burrs cleaning. If you are buying Starbucks (or similar) beans then the single biggest upgrade you can do is to start buying quality beans from a specialty roaster. Its not as hard as it was a few years ago to get dark roast from a proper specialty roaster when the fad was for almost under roasted beans, thankfully that trend is drawing to a close.

Dark roast only I would only consider conical personally. The best flat burrs for dark roast just emulate the output you getting by default from most conical burrs, so why not just get the ones made for the job in the first place?

I am not sure what your budget is but something like a Helor Flux would be similar pricing to the DF83 and the Flux comes with immense 73mm Mazzer burrs that are hard to beat for dark roast. Only downside is that its a hand grinder, and take about 45 seconds to grind an espresso sized set of beans. I hand grind both espresso and pour over when I am not at home and its manageable if you are not doing too many shots back to back.

Otherwise the bigger conicals with a motor tend to be a lot more than the DF83. I would really stay away from the Niche Zero (and its bigger brother), they are overpriced and just not good value in today's market. I used to own a Zero and its frankly disappointing for its price point, I sold mine and made nearly enough money to buy my (secondhand) DF83 with the upgraded burrs.

Something like a Femobook A68 would be around the same price as the DF83 and is motorized. I have not personally tried it, but it has decent reviews. I quite fancy getting one as another grinder (I have a Timemore 078 as well for pour over) for home for when I want dark roast as my setup is very much tailored to light/medium-light.