Well, if we talk about adaptation, there's some manga that already got a Drama CD (like audio-book or something like that) voiced by some popular voice-actor in Japan. There's also manga that getting LN adaptation and the otherwise (like Tate no Yuusha manga are more darker than the LN one even though the original one was the LN). There's also web-anime adaptation (ONA) kinda like streaming but on the original site of the works and usually made by indie production (the author and their circle or other, like Horiyama before adapted into TV-series)
The thing is, it depend on the author. Since, getting anime adaptation (especially the TV-series one) are really business things. Like, thinking about how much audience the anime will get, the revenue for the studio, things like that. I don't really wanna talk about it but, some author really don't wanna deal with that kind since it kill the feel when they make the manga or the worse, the adaptation itself ruin the manga. Well again, it depend on the author (Like Hiroyuki-sensei, although his manga are released in 2020, he pushing it to get anime adaptation, and really get it at 2021)
Also mine was Atsumare!, Boy's Abyss and Yankee-kun to Hakujou Gaaru (Delinquent and the White Cane Girl) because I can see if these series are getting adapted although there's many more in my library