We found out, that the Unipi package installation method doesn't work on Raspbian Stretch. We fixed the behaviour and also updated the Unipi Debian Repository page to include this new procedure as well: https://repo.unipi.technology/debian/. The process of installation of our packages should go much smoother now.

We have discovered, that in certain batch of Unipi Axon PLCs, the / partition was only 1.4GB large. There wasn't an easy way how to fix this and it required manual repartitioning of the /dev/mmcblk0 via fdisk. MervisOS version 2.3.0.10 and OpensourceOS 20200612.0 fixes this in a way, that flashing these images will create the partition structure from scratch. This behaviour is changed only for Axon images. You can download both images here. This change is already included in the Axon Node-RED image 20200610.8