"Is there a class of computers out there low-power enough to run for hours on a USB battery pack but significantly more capable (and perhaps more "standard", e.g. able to run GRUB2 and generic Debian) than the Raspberry Pi 5?"
Generally speaking, the class of computers you're referring to are "netbooks" such as the Chrome Netbook, which has been recommended. I had a Toshiba Netbook 10 yrs ago, which I bought at Best Buy for a few hundred $, ran a lightweight testing version of Debian distro on and bike toured over a month around Oregon with it in my panniers. It worked great, until I stepped on it in my tent one day... =( I'd suggest taking a look at System76's Lemur Pro for a few reasons. 1. It'll be very Linux compatible. 2. System76 is very supportive of Right2Repair. 3. You can customize it to your needs & wants. 4. At 2.2 lbs., under 1 inch thick when closed, it's very portable. 5. 14hr battery life. Just a few features that make this a good choice for remote workers. https://system76.com/laptops/lemur
