If anyone's wondering why Mihon looks slightly different than Tachiyomi, the reason is this is a fork of TachiyomiSY, which has some changes/features over Tachiyomi (e.g. a predicted next chapter release date).

What I wrote is all wrong. I've just looked through the commit history and Mihon is a fork of Tachiyomi and currently it doesn't have any changes besides branding and being Android 8+.

I don't know why I believed otherwise, but it might be F-Droids 3 months old Tachiyomi build, which lacked many features compared to up-to-date TachiyomiSY.