Hi KWCork,
I spun this up in the lab earlier, and ultimately the issue is that there isn’t a complete 1:1 Feature parity of what’s possible with Graph API vs Basic Authentication which used PowerShell (which you’ve quite rightly said is via the EWS mechanisms and is therefore now broken by Microsoft’s retirement of Basic Authentication).
Frustratingly, Microsoft have acknowledged the lack of feature parity but proceeded with this anyway. Public Folders are a prime example of this. It’s not one off behaviour by Microsoft either, like the time that Microsoft stated they had 1:1 feature parity with Teams vs Skype for Business, yet had no federation with consumer Skype amongst other glaringly obvious inconsistencies.
I am aware that there are finally OneNote APIs available, I don’t know if they’re sufficient for Veeam to use in their current state as Microsoft advertise them more for functionality such as using OCR on images etc. As VeeamON is next week, maybe we’ll hear something there (I honestly don’t know as I’m not a Veeam employee).
On your comment of EWS being discontinued, it’s still being wound down on quite a few tenants, basically big enterprises that can haggle with Microsoft! Skype for Business Online was supposed to be shut down in/soon after July 2021 but they’ve still got infrastructure running…
I underestimated how much I’d added to my test OneDrive since my last backup so this is going to take a while but I believe you can still export the data out from the backup which you could manually pull back in, but it’s certainly not a “1-click restore” that Veeam is famous for.