libopenconnect5 might actually be the better package for adding the recommend dependency.
I recompiled the openconnect and libopenconnect5 packages locally and installed them, but forgot to mention the libopenconnect5 package in my RFE/bug report. Installing the recompiled libopenconnect5 package is enough. I could then use the current openconnect 9.01-1 package in sid. Best, Andreas