Yes, voca is in fact built primarily for GrapheneOS!

Update to v0.1.4, and make sure you have a text to speech engine installed, we recommend sherpaTTS, get both on nostr:nprofile1qqs83nn04fezvsu89p8xg7axjwye2u67errat3dx2um725fs7qnrqlgpzdmhxue69uhhwmm59e6hg7r09ehkuef0a2g9gl.