I believe not.
Check the following article:
Any individual can try out the features of Microsoft PowerApps Plan 2 for 90 days, and incur no costs as outlined in the How do users sign up for PowerApps section. This option is available to any user in a tenant and cannot be disabled by an admin. After the user's trial expires the user will lose access to PowerApps Plan 2 capabilities.
If a person signs up for a 90 day trial of Microsoft PowerApps Plan 2, and you choose to not support them inside of your organization, they can in no way incur costs to your company. When an individual signs up for Microsoft PowerApps, that is a relationship between that individual and Microsoft directly, like any many public cloud services from Microsoft, such as Bing, Wunderlist, OneDrive or Outlook.com, and does not in any way imply that the service is provided by your organization.
Finally, if your company wishes to restrict the use of organizational-only data inside of Microsoft PowerApps, that is possible through Data loss prevention (DLP) policies. For more details, See Data loss prevention (DLP) policies.
Thanks for the feedback Michael !
But we found another misleading info on https://docs.microsoft.com/en-us/powerapps/signup-for-powerapps
Individual signup has been turned off
When trying to sign up for PowerApps, you may encounter the following message.
This could be because your organization has disabled signups for individuals. It could also be because you purchased Office 365 through a partner. Learn more.+
If your organization has disabled signups for individuals, work with your IT group to get a PowerApps license assigned to your account.
which gave the impression that we were able to disable the signups as on Power BI ...
We have all trial licenses blocked. If you look at Get-MsolCompanyInformation |fl AllowAdHOcSubstriptions if set to False then users cannot sign-up for trials. I have a user that is trying to sign-up for the PowerApps Trial and they are getting the "Sorry... We can't finish signing you up. Your IT department has turned off signup for Microsoft PowerApps. Contact them to complete signup". I'm working on how to give specific users access to the trial license but this setting does seem to apply to the sign-up for all "trial" licenses.
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