This could be helped with User experience - ALLNET ALL4781-VDSL2-SFP / Switch Modul (Mini-GBIC), VDSL2 - Omnia HW tweaks - Turris forum but then
Not sure what is to be bridged? Is one Omnia to be a Wifi repeater/extender for the Cisco Wifi and to connect to the Cisco via WiFi or wire?
Did you see Turris Documentation ?