Lightroom Classic 8.3.1
Whenever I eject a network drive, Lightroom Classic crashes and has to be restarted anew.
However, if the network drive in question does contain any files critical to LR function, then that's not a bug - that's expected behaviour. So, you need to determine what LR-related files are on that drive.
Does the network drive contain any files such as the catalog, previews, or caches? As macOS is a form of Unix, you also need to be aware of any soft links to folders that may ultimately result in critical files being placed on the network drive.
I haven't checked, but I'm guessing LR 8.3.1 has the same restriction as earlier version (i.e. certain files should NOT be placed on network drives - they must be on either internal or USB/Thunderbolt-attached storage). While you mentioned earlier versions of LR never crashed when the network drive disconnected, we can't assume you've just done an in-place upgrade to 8.3.1 - we have to rule out any potential storage reconfiguration that may have been done.
If it's still crashing and you don't think you have any files critical to LR function on the network drive, then I recommend contacting Adobe Support.
Hope it's sorted soon...
We could not find any crashes reports tagged with your email address registered on this forum. If Lr crashes next time, add your email address in the crash report so that we can identify your crash report and debug the issue.
You can reference https://helpx.adobe.com/photoshop/kb/submit-crash-reports.html for more details.-Satish