Try looking at ARM Embedded Single Boards. They're only ever marketed to industry for smart automation/IoT systems, but effectively fill the niche you're looking for: https://uk.farnell.com/c/embedded-computers-education-maker-...

I've saved a few during my years of lab management as they ran our infrastructure, and they're cracking PCs. Sometimes I run into fringe issues with drivers, but never anything major. Pretty much all validated on Linux OS too, so better support than most client PCs.