On the main app page is a green and white Lemmy (top left). Tap that. There is a link in the context menu called "remove ads" with a thumbs up emoji.

You need to be on version 25 or newer for the option to appear.

On the main app page is a green and white Lemmy (top left). Tap that. There is a link in the context menu called "remove ads" with a thumbs up emoji.

[EDIT]

You need to be on version 25 or newer for the option to appear.