There's a workaround suggested in another thread which worked for our project and team.
So to reiterate: Comment out the entire method AkWwisePicker.OnEnable() - I'm not sure what this breaks and how bad that is, but it allows you to boot up Unity again, and the "Populating Wwise Picker" progress bar will still work in other situations once you're already loaded up into Unity Editor.
It's all kinda murky 'cause the whole system that the Wwise Integration is running to migrate from an old way to reference Wwise project structures (Events, SoundBanks, etc.) in Unity to a newer way to reference the same things. I understand why they're doing that (the newer way should be less susceptible to how some earlier Wwise Integrations kept losing references in Unity Components/Scenes/Prefabs, also the new way should be able to handle something like if you rename an Event in Wwise project and regenerate the SoundBanks without breaking references in Unityh). What I absolutely do not understand is what the migration process is that is being done while upgrading the Wwise Integration from Wwise Launcher. I don't know what it is when Wwise keeps doing that thing automatically to "Populating Wwise Project"
a) why those processes need to be undocumented and unexplained
b) why they are automated and not run manually via Wwise Picker button like "Refresh Project" or via a MenuItem like the one you open Wwise Picker from, like they could have "Window/Wwise/Migrate GUIDs in Scene to ObjectReferences" and "Migrate GUIDs in Project to ObjectReferences" etc.
c) why do they repeat the process for the same Scene every time you open it? If the Scene was processed already and all Ak.Wwise type fields now have ObjectReferences instead of old per-object stored GUID values, why is the Scene always marked as dirty and changed and Debug.Log messages created every time for objects that were migrated? Why isn't the upgrade migration done during the Wwise Launcher "Upgrade Wwise Integration in Project" not enough?
I strongly feel that this process needs to be explained better, should have options to turn it off, should not mark Scenes dirty if nothing was changed (everything was migrated already previously), etc.