For me it was the open source e-ink display TRMNL[2] which I learned about via ATP and Snazzy labs[1].
1. https://youtu.be/eIcZZX10pa4?si=deMGwccwwO4wJdBe
2. https://usetrmnl.com
1. https://youtu.be/eIcZZX10pa4?si=deMGwccwwO4wJdBe
2. https://usetrmnl.com