One thing that doesn't come up here yet: our partners RBZ have developed an open hardware alternative SOM for MNT Reform based on NXP LS1028A with 2 Cortex-A72 cores and 8 or 16GB RAM. This is currently in the first bringup phase, but sources are already released:

https://source.mnt.re/reform/mnt-reform-layerscape-ls1028a-s...

I'm also personally working on a Kintex-7 (FPGA) SOM. This will allow us and others to implement RISC-V or other architectures, incl. retrocomputers and carry them around in a laptop form factor.