A great example of an app I use daily with seamless UX design is Spotify. Like so many people now-a-days I am in the habit of listening to music throughout most of my day - on the way to/from work, while at work, when I'm relaxing or hanging out with friends... needless to say, music is a big part of my life and Spotify makes it easy to access my music from anywhere, any time, on any device.
To start off with, the app interface is easy to use. When you first open the app it has your recently played playlists and music you had listened to recently so you don't have to search them out every time you open the app.
A quick scroll down reveals more playlists that Spotify has made or recommended for me based on my listening tastes. It does the job of curating my favourites and introducing me to new artists/songs without me needing to do anything but tap the play button.
The search function is simple and easy to use and if you aren't looking for a particular song/artist/podcast you can decide to browse one of the popular genres instead.
Arguably the most important screen of the app. This is where you will spend most of your time while on Spotify and requires the most seamless UX experience (which I think it achieves). You are able to pause, skip, shuffle or repeat the song with ease and you canthe song to save to your Liked Songs playlist. There is also the option down the bottom left of the screen to change the device output (to switch between a laptop, phone, smart tv or speaker).
And finally, the 3 tabs at the bottom make it easy to switch between the 3 main sections of the app: The home screen, search function and your own library of songs. The limited options make the UX flow really clear.
Overall, I always find my experience with using the Spotify app seamless so I can spend more time listening to music I love and less time trying to wrangle my music collection into some semblance of order.