On the "little machine for custom jobs" front, can anyone suggest a low cost subnotebook, x86-64 or ARM (i.e. Chromebooks OK) where I can wipe the Google software and install some version of Ubuntu? I've been using EeePC Seashell machines for that for years, but they're wearing out and I need something close to current production.
I'm looking for a machine where there's not too much difficulty doing this. That varies with the machine. Some require removing a jumper to let you overwrite the OS. Some require overwriting flash memory with somewhat sketchy binaries.
I suggest picking a machine from https://mrchromebox.tech/#devices , filtered to the ones that support the full "UEFI Firmware". Conveniently, this also lists the needed method to make the firmware r/w if you care about that. Of course, this depends on you considering MrChromebox non-sketchy, but he is AFAIK reputable and if you prefer all the source is on GitHub.
Oh, and annoyingly I suggest that you avoid ARM Chromebooks; firmware support and OS options aren't there (yet, I dearly hope).
It's not as small as your EeePC, but I very much enjoy my PineBook Pro [1]. I'm running Manjaro Plasma KDE on mine, and I can do just about all I want, dev wise on it: docker, ddev, vscode, firefox, chromium, LibreOffice, etc. It's about as powerful as a mid-tier Chromebook.
I have a Thinkpad X120e Chromebook that still kicks with Gallium OS on it. I think you can pick those up for about $50 USD now. There's a Chromebook version and a "regular" version.
The older GPD Micro PC can be found for a bit cheaper than their newer ones. But they're likely more expensive than you are looking for I think! Though on the other hand, they're very easy to run whatever OS you want on them
On the "little machine for custom jobs" front, can anyone suggest a low cost subnotebook, x86-64 or ARM (i.e. Chromebooks OK) where I can wipe the Google software and install some version of Ubuntu? I've been using EeePC Seashell machines for that for years, but they're wearing out and I need something close to current production.
I'm looking for a machine where there's not too much difficulty doing this. That varies with the machine. Some require removing a jumper to let you overwrite the OS. Some require overwriting flash memory with somewhat sketchy binaries.