Why do you have the restriction to original work and public domain work "with your own take"? For me, personally, that's a bit disappointing, since I work largely on digital reproductions of public domain work leaving it "as is".
One of my leisure time pursuits is to find interesting old books on cavalry, making them into high-quality reflowable e-books. It's a lot of work. I sometimes have to find multiple originals in libraries and antiquarian bookstores if there isn't a single original available in a good enough condition. Then I type them in multiple times to make sure there are no typos. I scan & vectorize the graphics. Then I produce nice reflowable EPUBs and ensure compatibility with a wide range of hardware. That kind of thing is hard work, and yet that sort of work is probably not protectable by copyright. It's been a personal frustration of mine that platforms for bookselling are often so uninviting towards that kind of content. -- It would be pretty easy for me to take a work like that and make it into an edition "with commentary", but, honestly, I'd much rather allow these works to shine in their original glory.
A kit was for sale here: https://forum.thinkpads.com/viewtopic.php?t=122640
Edit: better wording
Unfortunately, I just don't think a free open source phone will full modern functionality is ever going to exist.
How is it at all possible to certify that data has been deleted and no copies were taken..?
https://youtu.be/1Nh_vxpycEA