ARM64, at least, is moving towards UEFI/ACPI for booting/peripheral support, so ideally a lot of things will "just work" once people are shipping mobos/silicon

ARM64, at least, is moving towards UEFI/ACPI for booting/peripheral support, so ideally a lot of things will "just work" once people are shipping mobos/silicon with it enabled (and they already are). That said it's unclear what the volume on those parts will be once higher-grade CPUs come out, which will impact pricing/availability. And newer parts are going to be necessary for competitive performance/power. If the only place you can get a 14nm Thunder X2 is some high-end SuperMicro workstation, it'll be somewhat limiting in the end, anyway. (You can buy a Thunder X1 prebuilt desktop on the order of $1500 USD right now, at least.) ARMv7 of course is a different bag of worms; Mali tends to ruin everything. But if you can avoid it, a lot of systems can get by with upstream U-Boot and upstream Linux... You can even get some cheap Asus chromebook laptops that can run libreboot and upstream everything (including WiFi if you buy a dongle.)