Greasy Fork is available in English.
Shows all pages at once in online view for these sites: Alandal, Batoto, BilibiliComics, ComiCastle, Comick, Dynasty-Scans, MangaStream WordPress Plugin, Asura Scans, Flame Comics, Rizzcomic, Voids-Scans, Luminous Scans, Shimada Scans, Night Scans, Manhwa-Freak, OzulScansEn, AzureManga, CypherScans, MangaGalaxy, LuaScans, INKR, InManga, KLManga, Leitor, LHTranslation, Local Files, LynxScans, MangaBuddy, MangaDex, MangaFox, MangaHere, Mangago, MangaHosted, MangaHub, MangasIn, MangaKakalot, MangaN
This script doesn't have an option to limit pages loaded yet so it will load everything. There is also a version that allows for viewing as double page spread on this site which can search for(shameless advertising :p)
Can Manga onlineviewer loads all pages?
Can Manga onlineviewer script loads all pages at a time instead of maxium pages loaded is 10?