They're using an app which has an ad-supported version. I prefer Jeroba, which is only donation supported, but I'm not gonna stop people from making decisions.
They are using an app, which isn't great. Most of the aps don't do formatting correctly, which is a VERY low bar considering how much of Lemmy is text.
Sync does formatting correctly. I came to Lemmy only because I like Sync so much. I paid for the lifetime version of it with Reddit and will probably pay for the lifetime version of this eventually. To each their own wrt how Lemmy is viewed, I guess.