
1.Before migration, you should prepare SharePoint Migration Tool, a SharePoint Online tenant, a account with administration permission in both SharePoint Server and SharePoint Online.
Reference:
Migrate SharePoint Server sites and content
2.You cannot convert home page to communication site.
3.Modern team site with Office 365 group Vs Modern team site without Office 365 group.
(1)Office 365 group extends SharePoint team sites to include additional Microsoft 365 applications for collaboration using simplified permissions, which includes shared Mailbox, shared Calendar, shared OneNote and other collaboration tools.
Use this type of team sites:
- Increased flexibility to adapt to organizational changes.
- Simplified site management.
- Simplified permissions management.
(2)SharePoint team sites without Office 365 group just only have permissions for SharePoint. It meanings that use team sites without Office 365 group if you only need a place to share documents, links, images and don’t require social collaboration tools.
Use this type of team sites:
- Allow organizations to adopt the benefit of the modern SharePoint interface without the additional governance considerations of groups or teams.
- The SharePoint security group is directly responsible for security management.
References:
5 Reasons to Use Office 365 Groups for Team Collaboration
Office 365 Groups or SharePoint Team Sites?
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