My experience is that 90% of the work on these projects is integration: getting the toolchain working, and all the pieces talking. If there were an easy-to-use digitizer and a documented toolchain, I'd buy a LilyGo T5 right now.

Without that, I suspect I'll never get around to making one work, and I'm not buying another half-started project.

As a footnote, 50% of the remaining work is on the stupid stuff like cases and power supplies. I'm glad you did that. But if you ever sell this as a device, consider provide a variety of cases for different use-cases (desk stand, wall mount, metal box with room for other stuff, etc.) and your sales will double.

As a footnote, I like when devices are compatible with something standard, like a Micro:bit or a Circuit Playground. That guarantees a basic working toolchain for at least getting code on, as well as a support ecosystem.