Could you specify which of the partitions are considered firmware partitions, are we talking abl.img, aop.img, bluetooth.img, core_nhlos.img, dsp.img, dtb.img, modem.img, qupfw.img, tz.img, uefisecapp.img, xbl.img and so on? 
If that’s the case, here’s the situation for the available custom ROMs at the moment
| Firmware | ROM |
|---|---|
 |
CalyxOS (version 3.3.2) |
|
/e/ (version 0.23) |
|
iodé (version 2.4) Edit: Firmware only missing in 3.0 beta |
 |
LeOS-S (Firmware folders empty, no idea how GSIs work  ) |