Building Ungoogled Chromium for older Android versions

Ungoogled Chromium is a very good browser without Google dependencies. But the Google Play available version is only for Android 5.0+. See github.com/ungoogled-software/ungoogled-chromium-android

I tried to find it out, but found nowhere, how to try to build Ungoogled Chromium for Android 4.4+. As far as I know, the newest version of Ungoogled Chromium don’t use any sepcific Android API 21 (5.0) features.

Please help me, which steps I need to build the Ungoogled Chromium for Android 4.4+ or Android 4.1+.