This is a semi-old request but I'm chiming in that, as an educational tech employee who is soon to be retired, and hoping to "gig work" as a developer for my former employer, I would need to build apps with my personal account.
I'd also like to build my own "personal productivity" apps using data from the Office365 subscription that I will have to buy after I retire.
So yes, please let us build apps as non-work and non-school accounts!
Microsoft has a nice video about what happened to a security guard at Heathrow airport after he discovered Power Apps.
I'm amazed that he was able to do what he did:
Being able to use a personal account for training and development would be very helpful.
I'm having a miserable time getting to know Power Apps with a work account. For example I've just managed to add Power Apps Community Plan to my work account, but can't do Power Automate - when I go to Flows the canvas is blank and there is no menu to create a new flow.