Thanks for your hints, I already know it.
After some experimenting I found that I have to set both IP address (of computer, on which is Boinc Manager running) and password, to be able to connect to Boinc client on Omnia (documentation was not clear in this)…
Then there were difficulties finding project which will run on Omnia - I tried some of them, but some were not able to connect to project at all, some connected to project but didn’t got tasks; in the end no one was able to compute any task, even though I played with settings of preferences… I got quite tired and down so I interrupted experimenting for a while 
.
By “I will connect from another computer to my Debian” do you mean Debian on another PC or Debian in container on Omnia? If the later is the case, could you kindly specify which project do you use and how you set computing properties? I’d check and try again 