Wait for the compatible version.
When Apple makes a major change in their OS you can anticipate a lag in compatibility across audio and MIDI drivers. You will still observe “do not upgrade to OS 11” warnings on many audio software websites, until testing and verification is complete.

MACOS 11 Big Sur Compatibility Guide

Thanks.

I'm aware of this practice when dealing with audio/MIDI hardware compatibility for OS updates. That's fine. My questions are:
1. Is this a known issue specifically Big Sur for the MODX driver? I'm asking as I don't remember if it's used to work after I upgraded or not.
2. Is there a release date for a compatible driver?

... although this doesn't cover the drivers specifically or MODX - it can provide some insight into what's happening with software dev, testing, etc.

https://helpcenter.steinberg.de/hc/en-us/articles/360017403100-macOS-Big-Sur-and-Apple-Silicon-product-compatibility

Many items are under test - so it would appear the situation is fluid at the moment.

As of yet, there is not a driver available that supports MacOS 11.

https://www.steinberg.net/en/support/downloads_hardware/yamaha_steinberg_usb_driver.html

From Mac OS 10.13.6 onwards, Apple has been having enormous trouble reigning in some terrible design and implementation decisions around the T1 and T2 security chips and coreaudiod, a process that runs in the background all the time, mainly monitoring inputs.

You might think "what do security chips and audio have in common?"

The answer is two fold:

Microphone monitoring and USB security checks are done by the T1 and T2 chips, in a closed off (secure) manner that users can't fix. And it seems Apple can't fix, either.

The microphone issue causes all sorts of volume problem and audio quality issues, that's still not fully sorted, even in the latest Big Sur and current Macs.

The USB issues are legion. Absolutely enormous plagues to productivity.

Your best bet is (if you can) rolling back to 10.13.6, as this has the least problems, as they were trying to do the least with the T1 and T2 chips back then.

... not to mention T2 is paper thin security due to the exploit defeating T2's original security purpose. So if it's part of the (audio) problem - it's also no part of any solution apparently (meaning security). The information I read some time ago was that it couldn't be fixed or patched (in existing hardware). I'm not sure if that assessment has changed.

T1, at least, seems not to have this same security flaw. So any impact on audio - at least T1 is otherwise not sleeping on the job.

Thanks for this warning. I have to stay on Catalina for now!

Competitively, another flagship synthesizer from a different manufacturer has MacOS 11 drivers available with (claimed) compatibility to both Intel-based and Apple Silicon (M1) systems.

Competitively, another flagship synthesizer from a different manufacturer has MacOS 11 drivers available with (claimed) compatibility to both Intel-based and Apple Silicon (M1) systems.

These will not work for the MODX/MONTAGE so they are of no importance here.

I didn't even give specifics about which manufacturer or device was supported. There is relevance in a Ford vs. Ferrari kind of way. Hopefully given we see others can release compatible drivers in 2020 (using the same information provided by Apple) - we can see some movement to catch up.