Marvel Comics has its own digital comics shop. It is powered by ComiXology, and it looks like they are getting ready to close it.
Thank you for being a loyal Marvel fan. As a fan of Marvel digital comics, we wanted to let you know that the Marvel Digital Comics Shop at comicstore.marvel.com will be closing on June 2, 2020.Marvel Comics
As I mentioned, it is powered by ComiXology, and any digital comics you have bought will continue to be available to read on the ComiXology app.
I have a feeling that they are going to concentrate on their Marvel Digital Unlimited app, the ComiXology app is the go-to for the comics.
Please visit https://www.marvel.com/help/category/24 for more information.