I've tried the preview version as per this suggestion:
https://powerusers.microsoft.com/t5/PowerApps-Forum/Share-an-app-with-a-group/m-p/37126#M15402
However I'm sill told I can't share with this type of group.
Obviously a distribution list isn't a security group - but surely you can simply enumerate all users in the group and then add them individually to the share-list?
Even the outlook add-members-to-group function allows you to copy/paste a whole bunch of users and then select them one-by-one. Not ideal, but still better than typing each name individually.
Kind regards,
Russel
An update this feature has been started and isn't far off!