https://www.privacyguides.org/en/android/?h=apk#obtaining-applications

a good open source apk workflow is this:

git apk (signed from dev)/accrescent > neo store (use official repositories whenever possible) > google play

use #obtainium to track and keep apks up to date. it's awesome

https://github.com/ImranR98/Obtainium

and i recommend #molly (a hardened fork of signal).

https://molly.im/

get it on #accrescent and it will auto-update direct from and signed by the dev

https://accrescent.app/

that should get you started 🤙💜