Perhaps not exactly what you are looking for, but there are Smart NIC PCIe cards running Linux (usually for data center applications), see e.g. these links:

https://datatracker.ietf.org/meeting/105/materials/slides-10...

https://legacy.netdevconf.info/0x14/pub/slides/39/Netdev%200...

https://smartnicssummit.com/proceeding_files/a0q5f000000lcIn...