There aren't any open commercial FPGAs as far as I know. Some have had their bitstream formats reverse engineered though.

We're starting to see open source FPGAs but they are miniscule: https://tinytapeout.com/chips/ttihp26a/tt_um_fabulous_ihp_26...

Not many options unfortunately. Today that's GateMate.

Next best thing? The mature reverse-engineered families nextpnr[0] supports.

0. https://github.com/YosysHQ/nextpnrhttps://github.com/YosysHQ...

I think Efinix did something internally, with Yosys.