There are a lot of mobile clients for Lemmy. The web interface is not that great in my opinion, so a mobile app is kind of needed. Some of the more popular ones:

• Boost for Lemmy (Android, beta version)
• Liftoff (Android and IOS)
• Voyager (web application but has IOS app in Testflight)
• Jerboa (Android)
• Connect (Android)
• Thunder (Android and IOS)
• Mlem (IOS)
• Memmy (IOS)