Well, you caught me while I'm finally installing SampleTank4 MAX and I'm guessing that you don't have the full version of Kontakt, so, excluding choirs, these come quickly to mind:
Soundiron has Mimi Page Shadows & Light, Voice Of Wind Adey, Voice Of Wind Kimba, Voices Of Rapture, Voices Of Gaia, Voices Of Rage, for the free Kontakt Player. Type "Voice" into their search line to get links.
Soundiron Virtual Instruments
Heavyocity has Vocalise 1, 2, and Mosaic Voices for the free Konakt Player.
Heavyocity Vocalise | Vocal Effects Synthesizer VST
Heavyocity Vocalise 2: Vocal Instrument VST Plugin Software
Heavyocity Mosaic Voices: Choir Virtual Instrument | Vocal Chorus VST
Output has Exhale for the free Kontakt Player and its web service Arcade which has loops/instruments online.
Exhale ™ - A Modern Vocal Engine | Output
This brings up the topic of loop/sample online services, which usually have some way of slicing/stretching/playing/editing/manipulating their loops to taste. A few examples (usually have a free intro trial for free with a sign-up):
https://output.com/arcade
https://www.loopcloud.com/cloud/subscriptions/plans
https://sounds.com/samples
https://www.magix.com/us/music/music-maker/loops-unlimited/
https://www.noiiz.com/?utm_source=samplephonics&utm_medium=home_page
Realivox has Realivox Ladies (complete, light or Theresa) and Realivox Blue for the free Kontakt Player.
https://realitone.com/
Zero-G has Vocaloid instruments/libraries.
https://zero-g.co.uk/pages/search-results-page?q=vocaloid
East-West has a number of vocal libraries (purchase or subscribe).
Hollywood Backup Singers, Voices Of Opera, Voices Of Soul, Voices Of The Empire, and Voices Of Passion.
http://www.soundsonline.com/Vocals
Best Service has a number of vocal libraries for the free Engine2, including Era II Vocal Codex. It also has Altus and Kwaya for the free Kontakt Player.
https://www.bestservice.com/era_ii_vocal_codex.html
https://www.bestservice.com/altus.html
https://www.bestservice.com/kwaya.html
Ueberschall has this vocal loop library for its free Elastik3 player.
https://www.ueberschall.com/en/product/125/Adlibs
Big Fish Audio has Momentum for free, a loop/sample player/editor/slicer/manipulator that works with its (and mostly all other) loop libraries, including vocal loop/sample libraries. This is probably not a bad thing to have in your arsenal and maybe even a good place to start.
https://www.bigfishaudio.com/momentum.html
Good luck & stay safe,
Paj
8^)