Convert digital manga (or comics) to .cbz or .cbr file format, copy them to my Android tablet, then I use a bookshelf app called Perfect Viewer to read them.
I can do this on my Android phone too, but the screen is too small for some of the more detailed comics, so I prefer my 10" tablet for reading. An example of the latest things I've been reading:
I've been using the manga plus app on the Google app store, and it's pretty good. I pay like 2 bucks a month and get to read jjk, chainsaw man, MHA, black clover, undead unluck, and some others that are less well known. I'm sure there's a better (or free) app, but I have yet to find it. I think Boruto/Naruto, bleach, and one piece are also on there.
Tachiyomi with (mostly) Mangadex (well, one of its forks anyway), Manga Plus and CDisplayEx/Kuro Reader for digital stuff I bought on Kobo and removed the DRM from.