I’m mildly surprised that this isn’t an official product. I have half a dozen relatives I’d give “AirFrames” to if Apple made them or let a third party do it, especially if they had decent handling of Live Photos.
The keywords that you would want to enter into your preferred search engine are: Digital Picture Frame At this point in time that is already a regular product category. The OP could just have bought one, but chose the DIY path.
All of this should be one step. Ideally Like airdrop. I say "share" and it should magically show up on the photo frame. I should be able to download pics from reddit/imgur and display it on photo frame using a CLI/API.