Nobody knows. I have tried to get answers on this and not been told anything definitive, just vague responses that don't address the question directly.I'm fairly certain Microsoft would love it if everyone just bought Power Automate per-user plans so they make the multiplexing requirements pretty onerous.My understanding though (which is probably wrong) is that if you hold a stand-alone (premium) license and create a flow with an approval in it, then anyone who receives that approval (interacts with the flow) will need to also have a per-user license, or the flow itself can have a per-flow license. I don't know whether there's any distinction between a flow built by a premium user that actually uses premium connectors or does not.Safest bet to stay on the right side of MS licensing is create your approval flows under an account with standard M365 licensing and use your premium account to track/audit approvals.
I still don't know how far they go with multiplexing when it comes to things like retrieving a table from a premium data source and emailing it from the flow as an HTML table. Does every recipient of the email need a per-user plan or a per-flow plan for the flow? Who knows? If it's possible to do so, use Logic Apps to avoid this doubt.