The only way I know to make it work on any app is to go into your Lemmy account settings and uncheck the show read posts option and save.

So, scrolling past marks the posts as "read" but that won't hide them. The way I do it is to use the "hide read" button in the more options menu where the settings button lives. Alternatively you can use that other setting to automatically hide all read posts, but I can't find that setting either...