100G LR4 link won’t come up between N9K-C93180YC-EX and MSN2010

[edo1]

I’m trying to link a Cisco N9K-C93180YC-EX (NX-OS 9.3(14)) to a Mellanox MSN2010 (Onyx 3.6.8008), QSFP-100G-LR4-S transceivers.
100G LR4 (QSFP-100G-LR4-S) links between Mellanox switches (MSN2010 — SN2700M) work fine, but Cisco N9K-C93180YC-EX — MSN2010 does not: the Mellanox port comes up 100G and flaps, while the Nexus port stays “link not connected”, never flaps, 0 RX/TX. Optics on both sides show good enough Tx/Rx power. Speed 100G, no-FEC, autoneg off on both ends.
Has anyone seen this Cisco–Mellanox LR4 interop weirdness and found a working combo (Onyx/NX-OS version, etc.)?

 

[i386]

Try to enable fec91/rs-fec in both switches for the port that ist used

 

[edo1]

@i386 cisco doesn't allow me to do this

switch(config-if)# fec rs-fec
ERROR: FEC validation failed on eth1/53 due to incompatible configured speed or transceiver type

 

[Jelmer]

No RS-FEC on N9K-EX 100G as far as I know, FX does.