I'm running 2 x old Studio Live consoles (SL16.4.2 and SL16.4.2AI) which both stopped working through firewire when my 2014 MacBook Pro updated to BigSur. It was working fine on older versions of IOS. I requested info from Presonus and this was the response. I'm yet to give it a try but I'm expecting that it is an IOS problem which will be rectified when I take my computer back to Mojave.
Thanks for getting in touch.
The StudioLive 16.4.2 will not work on any OSX past Mojave, the AI mixer will work on Mojave so that is the OSX you would need to install to have everything working.
Live Sound Support Manager