Common reports used for O365 Tenants

Here are the list of common generated reports that are typically used in organisations –

a)       Site Collection Details –

S.No	Site Collection Name	URL	Size in GB	Rootweb template	Primary Owner	Secondary Owner	Business Unit	Subsite count	Rootweb list / library count	Site level workflow present (Y/N)

b)      Site level details

S.No	Site Name	URL	Primary Owner	Secondary Owner	List / library count	Workflows present (Y/N)	Forms present (Y/N)

c)       List details

S.No	List Name	List Type	Custom Forms(Y/N)	Contains Workflow (Y/N)	Workflow Name	Item Count

d)      WF details

S.No	WF Name	Site URL	List Name	Business Owner	Technical Owner	Solution Name	Complexity

e)      Form Details

S.No	Form Name	Site URL	List Name	Business Owner	Technical Owner	Solution Name	Complexity

f)        Solution Details

S.No	Solution Name	Site URL	Business Owner	Technical Owner	Solution In use? (Y/N)	Business Unit	Description	Dependencies

g)       Flow / Power automate & Power Apps

While the above tables talk about classic forms & workflows, you would want to have details captured on Flow & PowerApps on the tenants.
Here is a link to a blog post which talks about getting details on the PowerApps & Flow –

https://powerapps.microsoft.com/en-us/blog/admin-app-report/

https://powerapps.microsoft.com/en-us/blog/powerapps-enterprise-deployment-whitepaper/