The crash loop manga reader is still there on ipad mini 5th gen on ios 15.0.1 with Firefox 38.0 and Safari. I have more time to test things out this time. The tests below is using Faraway Paladin manga.
This is with FF:
ipad in portrait mode when the page loads (single page, side page advance): the loop appears.
ipad in landscape mode when page loads (double page, side page advance): no loop! but tiny images make my eyes bleed...
ipad in landscape on page load, switch to single page (still side page advance): no loop.
ipad in landscape on page load, switch to single page, turn ipad to portrait mode: no loop.. for 5 - 6 pages, then crash.
ipad in landscape on page load, turn ipad to portrait mode (reader automatically goes from double page landscape to single page portrait): no loop through end of chapter. I tried this with another chapter, so there shouldn't be any pages in history.
Using Safari, I get similar results as FF above, except the "switch to portrait" trick does not seem as reliable. I went through 2 chapters in FF without problems, but crashed first of 2 on safari. The safari crash was hard (restarted ipad), so maybe something in memory was cleared out letting the 2nd run complete.
As before, iphone se on 15.0.1 does not seem to have this crash, but I did not test as much due to the tiny screen.