If you do a little research and figure out how to get it setup you can share that knowledge with your boss. There are SOME things that could depend on how IT or the SharePoint owner configured things - like at my job there’s one SharePoint where they turned off linking it in my OneDrive - but otherwise you should be able to get it close to how it used to be.

It’s definitely silly for your boss to keep it all in his onedrive and sharing it out. OneDrive is supposed to be personal storage that you CAN collaborate on. SharePoint and Teams (basically SharePoint on the back end) are where team-wide storage should be. But, having gone through a transition to M365 I understand they probably just don’t understand and did what they thought they could.