Although there are no specific piano tabs, you can switch any Pro and Official tablature to notes, and see the musical notation instead of the fretboard. The standard notes can be enabled in Settings under the three-dot icon in the top-right corner on a tab’s screen. Here you can find a more detailed instruction on how to enable standard notation in Ultimate Guitar: Chords & Tabs.
As Pro tabs contain different instruments, you can find the actual piano part in the songs that have them.
Please note that at the moment the piano notation is only available in mobile apps, but it will come to the web version soon. If you’d like to participate in the beta, please visit this page: https://www.ultimate-guitar.com/forum/showthread.php?t=1922256
If you are a proficient piano player, you can use the chord tabs. An option to show piano chords diagrams isn’t present in the app, at least yet, but if you already have them memorized and know how to play, you can use the chord tabs as a reference to play the songs on the keyboard along with the lyrics.