Forum Discussion
Remove Microsoft Flow from SharePoint Modern Lists
From GUI NO you cannot do that but there is a workaround, don't Assign Flow License in the O 365 Admin Panel.
It still throws an ugly error if someone clicks on it in the Modern UI.
The Set-SPOSite PowerShell cmdlet has a parameter you can pass called "DisableFlows" but this would be done at a site collection level.
Some additional info...
In the uservoice, there is request to disable Flow for a site collection: https://office365.uservoice.com/forums/273493-office-365-admin/suggestions/15619065-option-to-disable-flow-and-powerapps
And it is impossible to block the usage of the Free Flow:
What is the Microsoft Flow Free Plan?
The Microsoft Flow Free Plan is used only for tracking purposes. Enabling or disabling it has no effect on a user's ability to create flows. If you disable the Microsoft Flow Free Plan, it becomes enabled again when a user logs in. This is the expected behavior.
https://docs.microsoft.com/en-us/flow/organization-q-and-a