Just wanted to add links to the avengers series example I gave, as this is true (from what I've seen) to every series on the platform now.

Avengers 2018 - | Individual issues series https://www.amazon.com/gp/product/B07KF5D89D?ref_=dbs_p_mng_rwt_ser_shvlr&storeType=ebooks

Avengers 2018 - | TPB/Collections series https://www.amazon.com/gp/product/B07JJ6FG1N?ref_=dbs_p_mng_rwt_ser_shvlr&storeType=ebooks

Both allow you to subscribe to them, so make sure you sub to the correct series for the comic series you want to sub to.