So users must be valid users, with a license to Dataverse within the environment that you speak off. If they have that, they would have have permission to the Flows.
But directly, you would share the SG to the App (not directly in Dataverse), because apps are shared in their own way.
as long as that security group (or however you have it setup) also give them access to the Tables in Dataverse you are good.
1. A license to dataverse simply allows them access to the environment
2. Security roles are required to define what access they have
3. Cutomizations of those security roles, defines what they can DO.
So imagine
Michael has a license to dataverase
You go to the Admin center, and click All Users and yep you see me.
I try to log into the App and it says GO AWAY
a) make sure you added me as a user or co owner at the App level, which will also share the connections
b) make sure you gave me at least Basic User role at the Dataverse level
c) make sure I have a dataverse premium license and or a Per App, Per Flow licenses
d) make sure that whatever Role(s) you give me, at least one of them has special privileges to the Tables that the app uses.
Meaning you go to the Role
Edit it
click on Tables
click on Customized Tables (if they are)
add the permissions that the role has
And bingo it all works :-)
Please please do not just give people System Admin to be lazy you will regret it one day
If this answers your question, please Mark as such and maybe a like.
Thanks!