As a Safari Web Extension, this app is actually intended for use alongside the ole' faithful web version of HN. I found myself in the same boat as yourself - trying other HN clients, but always coming back to the web version. But DAMN! the lack of dark mode kills... so I built this small CSS injector plugin to help :)

Speaking of which... I found a few minor adjustments that still need to be done w/ regards to the CSS rules (for example, reply links are still dark text in dark mode; oops).