Autism

Not even joking, I legitimately carry and use a mid-2000s PDA to help with that. It's not compatible with the MAJORITY of modern websites, it came with no games, can do mp3s and FLACs if you wanna allow yourself music, and the productivity apps it comes with are, while a touch clunky due to age, remarkably simple. No fluff, no distractions, just you and what you need from it.

Important dates and events go in the calendar. Tasks to complete go in the Reminders app. Shopping lists and general note taking I do with the Notes app. It's got a world clock with built in alarms. If I need any itemized lists for like daily/weekly chores, the Tasks app gives me a bullet point list of what I gotta do, even can do reminders.

Best part is that there's still folks helping to maintain software for these. PalmDB is an excellent website with tons of apps you can grab for free, with virus free cracks for old paid apps, that even works in PalmOS web browsers. I haven't yet found one for Windows handhelds (though there is a torrent on Archive with over 20 gigs of Windows Mobile apps and (probably virus filled) cracks), but both ecosystems can sync with modern OSes. I sync my Windows devices on my 2023-built Windows 10 PC.

I'm a retro handheld enthusiast, and my current daily driver is rare and expensive, but you can find Windows Mobile devices for dirt cheap. A Dell Axim X5 or HP iPAQ 2215 costs like $30-60, brand new factory fresh batteries are usually around $10-15, and there's even models with built in keyboards if you don't want to handwrite on the screen or use tiny resistive touch screen (think Nintendo DS) keyboards. Some external keyboards do exist, but you need drivers. If you want one with a built in keyboard, some PalmOS and old Windows Mobile 2003/5/6 smart phones have keyboards.