Apple just published changes to Safari at WWDC 2021 detailing a new feature called Tab Groups. But it seems to be more like other tab grouping solutions similar to Edge Collections. It will not offer multiple user accounts and full isolation like the FireFox Containers. Apple Safari will of course, sync the tab groups across iOS 15 and macOS Monterey systems.
Safari uses the current Mac user and there is no concept of switching users in Safari. You can enable Fast User Switching on macOS and switch between user accounts entirely. That's what I do with the family iMac so each family member has their own account.
Perhaps this fall, Safari Tab Groups will be close enough to what you are looking to accomplish. Minus the user account isolation.