[Aromasin]

You can absolutely do this using something like a CertusProNX from Lattice (I much prefer it to the Polarfire), mounting an SFP/SFP+ cage onto the FMC connector of the board, and wire their transceiver lanes to the FPGA SERDES pins. HiTech Global has a 4-port SFP/SFP+ FMC module. I believe there are also QSFP mezzanine cards but I haven't looked much into that. ISI or Trenz probably make something.

[bcrl]

I already have a 4 x SFP+ FMC board attached to my KC705, and that is what I have used for a bunch of development. However, that is the opposite of what I want to do. I want the FPGA to be inside of the SFP+ / QSFP module to be able to plug it into a switch without external hardware.

Microchip has an app note on putting a Polarfire into an SFP+ module complete with a board layout, but nobody is building them as near as I can tell. Lattice has a similar app note, but, again, they only sell the much larger eval boards.