Hello DmitryP,
Regarding the updates from the ERA server,
According to the second post on https://forum.eset.com/topic/3872-era-61-clients-not-updating-from-server/
the ERA server 6.1 does not support supplying updates any more.
You will either need to use the proxy server component, or have one of your windows computers become a mirror server. (configured via policy)
And no I have not figured out how to easily add the proxy server component to the Supplied image