Problems
A requirement to share some certificates and / or documents to the 3rd parties, notorious office 365 complex settings makes the whole configuration difficult.
Solutions
1. Navigate to Microsoft 365 admin center
2. Navigate to "Teams & groups", "Activate teams & groups"
3. Navigate to "Security" tab
4. Create a share group (if you don't have one) and add all desired members to the group
5. Navigate to "Sharepoint"
6. Navigate to "Policies > Sharing", expand "More external sharing settings", check "Allow only users in specific security groups to share externally", click "Manage security groups", add the group created in step 4.
7. Drag the share bar of the sharepoint to "most permissive"
8. Navigate to "Sites", create or edit existing sites, select the target site, select "Policies" tab, in "External sharing", select "Files and folders on this site can be shared with anyone". Then select "Permissions" tab, add the security group created in step 4 and all single members as site admin.
9. Share the folders or files in sites (by right clicking target entries) and select "Copy link", then "Anyone with the link can view"
References
- Sharing options are greyed out when sharing from SharePoint Online or OneDrive
- Manage security groups
