Install
Install Flint for Android 1.0.0 on your phone from the APK file on GitHub.
Flint is not in the Google Play Store. You install it from an APK, an Android app file that you download yourself. If you have not done this before, Installing apps explains how APKs and the "unknown sources" permission work.
Install the APK
On your phone, open the Flint for Android releases page.
Under the latest release, download
flint-1.0.0.apk.Open the downloaded file from your browser's downloads or your Files app.
If Android asks, allow your browser or Files app to install unknown apps, then go back and select Install.
Open Flint from your app drawer.
Good to know
The 1.0.0 APK is signed with a development key, so Google Play Protect may warn you that it does not recognise the app. This is the normal prompt for any app installed from outside the Play Store.
Update
Download the newer APK from the releases page and install it over the old one. Your bookmarks and history stay.
Uninstall
Press and hold the Flint icon, select App info, then Uninstall. This deletes Flint's history, bookmarks and settings. Files it downloaded are stored in Flint's own app folder, so Android removes them too; share or move any you want to keep first. See Bookmarks, history and downloads.