The problem is, trying to out-bright the sun on a battery-powered device is exactly as stupid as it sounds, and solutions such as transflective displays don't showroom well (someone should build a showroom w/ a light booth which simulates a bright sunny day and invite folks to try to use devices in it w/o shading them).
At this point in time, I'm seriously considering switching to a Raspberry Pi 5 as a daily driver (paired w/ a Wacom One 13 gen2 display w/ touch) --- if that display could be supplemented by (or swapped out for) an e-ink or similar daylight viewable pen-enabled display, it would probably push me over the edge (and yes, I've considered just pointing my Kindle Scribe's web browser at a page on the rPi --- if someone has a tool which would allow this to capture stylus input, please let me know).