Well, I guess I’ll give Harta a go. 
This sale, coinback and a new thread focusing on it combined to compel me to buy the available back catalogue…
月刊ビッグガンガン, currently my favorite 青年 magazine, is also having a １００円 sale going as far back as August 2016. Each ビッグ magazine has between 600 and 800 pages of manga.
Some of its series I’ve been reading have been 薬屋のひとりごと, ゴブリンスレイヤー and the past BBC pick スーパーの裏でヤニ吸うふたり, but there’s a lot of fun in reading trial chapters from other series as well… indeed, if I only had more time.