TIL the [Moon+ Reader](https://www.moondownload.com/) Android app that I've been using to sometimes sneak in some epub reading, also has very good PDF support, including annotations (i.e. drawing on the page, which it saves into the PDF file) -- and no annyoing "page flip" animation! Which is pretty much everything I want to try out handling sheet music digitally instead of on paper.
Yesterday I tried entering rhythm and pitch separately (in MuseScore), it feels vastly more efficient than doing both at the same time. Also, using a midi keyboard for pitches is much more precise (which is not as surprising ;)
TIL there's an open source mobile-optimized keyboard (for android) https://f-droid.org/packages/com.dessalines.thumbkey/ I much prefer "actually big buttons / precise actions" to any kind of "predictive assistance"; there is a learning curve though.
Thumb-Key | F-Droid - Free and Open Source Android App Repository
A privacy-conscious keyboard made for your thumbs.