From the Readme of the HTTP library we use in the app:
The OkHttp 3.12.x branch supports Android 2.3+ (API level 9+) and Java 7+. These platforms lack support for TLS 1.2 and should not be used. But because upgrading is difficult we will backport critical fixes to the 3.12.x branch through December 31, 2020.
To make use of the new features from OkHttp 4.0+ and to remove some workarounds for Android 4, @maniac103 and me will raise the minimum supported Android version to Android 5.
Expect version 2.9.0-release to be the latest stable version with support for Android 4 (There will be a new beta version with a few small fixes before bumping the minimum supported Android version).
Old apk version will be always available via GitHub releases: https://github.com/openhab/openhab-android/releases
Edit: The PR has been merged.
I haven’t tracked OpenHAB for a while; and it’s a pity to read this.
My apartment has a wall panel (Astrum Inspinia), running the app. The panel is running Android v4 and of course there’s absolutely no way to upgrade it. So are you suggesting me to remodel my room now?
Another kickback is that many of these specialized devices run old Android versions. I don’t know why vendors just love it.
You can still download an older version of the app from GitHub.
I just bumped into this when I wanted to repurpose an older, Android 4 tablet for being used as an OpenHAB control panel/display.
Using an old version of the app may not be a very good solution because either introduces app version differences among the devices in your home (I woud like to have a display in several rooms of my home).
I may be stating the obvious but the OpenHAB Android app should be backwards compatible with older Android versions as long as possible.
Android 4 devices are still present in big numbers in the wild and because they are old, they are often selected for such DIY projects like mine.
Android apps of other home automation solutions like the Tuya Smart are available on Android 4. So should OpenHAB which is supposed to be a more open and more generic solution.
According to Security - OkHttp the library version for Android 4 lacks of TLS 1.2 and higher. TLS 1.2 is already insecure in some configurations: Transport Layer Security - Wikipedia
Therefore we had to use the latest version of okhttp or migrate to a different http client which is a tremendous task.
Depending on the UI you want to use, you could:
PanelViewer and browser (which are essentially the same), by the way, are bad options for older devices, since those are normally not html5-compliant.
I am even thinking about forking an official app and rewriting it to render habpanel natively on Android. Without custom widgets of course. But have no time for such an undertaking