Not sure about macOS (don't use it myself) but for Android I like these two apps:
Glider: https://play.google.com/store/apps/details?id=nl.viter.glide... (open source, also on f-droid: https://f-droid.org/en/packages/nl.viter.glider/)
HACK: https://play.google.com/store/apps/details?id=com.pranapps.h... (not open source afaik, but more customizable)
Try Hack on iOS and macOS: https://apps.apple.com/it/app/hack-for-hacker-news-developer... I don’t know about android but -for me- it’s the best on Apple system.
I have this great cross-platform reader. It's called Firefox. Works on MacOS, Android, and a bunch of other platforms.