Linking in Companion
The Bitfocus Companion module can drive linked control too: a single Companion action can target multiple cameras at once, so one button press adjusts them together. It's the same idea as in-app Link Groups, driven from your control surface.
Targeting multiple cameras
Most bit.ctrl camera actions (Record Toggle, EI Step, Shutter Step/Preset, ND Step, WB Preset, User Button, Lock Toggle) let you select which cameras they apply to. Selecting more than one camera fires the action on all of them at once.
Encoders
Rotary encoder actions (Shutter, WB Temp, Tint, EI, ND) can also target multiple cameras, so a single dial adjusts several cameras in step.
Setup
For installing and connecting the module, see Companion / Stream Deck.