imo the best source is a locally hosted komga server. Download/purchase manga for hi res copies from places like AB/nyaa/baka/etc, rip scanlations with something like hakuneko or fmd2. Place in a folder, install komga+komf, point it at said folder. Komga scans in manga, komf scrapes metadata from manga updates or MAL. Use the Komga plugin in mihon and your progress is tracked both ways.
Much higher res most of the time, better translations, faster, more reliable, no ads, no tracking, no downtime unless your shit breaks, consistent across devices, no worrying about sites going down, manga getting taken down because it got licensed or group drama or whatever, and if you get tired of your library you can still just jump to the mangadex plugin or whatever I guess
I am somewhat conflicted on manga piracy. On one hand you should buy manga because the sales numbers for titles that aren’t stuff like one piece are often reallllly slim. On the other hand companies like viz are really shitty and my understanding is that the actual mangaka gets very little money from English releases. My suggestion is to learn Japanese. そうすれば、漫画をすべて読めます