I'm a collector of things and lists of things. Here's a list of PCIe accelerator boards with CPUs you can run Linux on.

I have these:
#XeonPhi
#Bluefield

Looking for a cheap one of these:
#IntelVCA

I'd like to think it's possible on the
Broadcom PS225
AMD Pensando DSC-25

But no luck so far

This doesn't fit the category:
Asrock BC250
Octominer x8