What good SBCs or used enterprise ARM servers exist that aren't running antique/unsupported Linux/*BSD distros?
This board + 64c CPU bundle is 1.5k on Newegg. With PCIe4 you're in a different league IO-wise vs any Pi-style SBC.
https://www.ipi.wiki/products/com-hpc-ampere-altra
https://shop.solid-run.com/product/SRLX216S00D00GE064H09CH/
Nvidia Jetson AGX ( wow the prices went insane on these, got mine for 1k years ago )