Hi,
there is a solution out (Microsoft). This was posted on Macrumors (https://forums.macrumors.com/threads/big-sur-11-6-onedrive.2310591/page-4) and worked for me.
"Okay mine is now working. Here's what I did. I went out and downloaded the installer from the Microsoft site. You'll find it here, https://www.microsoft.com/en-us/microsoft-365/onedrive/download. It gave me a warning that it needed to close one drive (because I had my personal account running) then it closed and installed over the existing version. Afterward, I was able to add my second account, a business account. Looks like the version is 21.160.0808.0004"
After you install the the 21.160.XXXXX version (the link above), OneDrive quits itself and installs a 21.180.XXXXX version and restarts (so be a bit patient). After that you can add a second account (business/personal). It actually asked me to add/reconfigure the second account that was installed on my Mac.
I guess its a special version for Big Sur 11.6 as it seems to check the OS version upon its first start and then install the 21.180.XXXX version.