So what i use works is a bit different kind of task but it gets you out of bed…

https://f-droid.org/packages/com.sweak.qralarm/

Collabora has a quit well working Android APP https://www.collaboraoffice.com/collabora-office-android-ios/

And thats basically libre office

Best Promo-Video ever

If you plan on doing it on a regular basis, you might want to try latex. This is going to be hard on the first one or two poster but on the long run it can save a lot of time…

You could check out https://plasma-bigscreen.org/ I never used it my self but it looks quite cool