It is possible to enable SMB Multichannel through the SMB config, but there is no way to check if it is working (AFAIK). Since Samba 4.13 it should even auto-detect RSS capabilites. Not sure about RDMA. But finally we don't know if the auto-detection worked.
Lets say we have four 1G ethernet ports in our server, while our windows client could have one 10G port. We expect >400 MB/s transfer speeds, but it does not work. Now we like to find the reason. Maybe some of the ethernet ports have RSS enabled and some not (mixed scenarios are not allowed for Multichannel) or maybe some adapters use a different IP ranges / vlans. Finally we won't find it out as long we start investigating the problem step by step or trial & error different "interfaces" settings, which is kinda frustrating.
That's why I like to see more output of the "smbversion" command which would return the used adapters, their detected capabilities, speeds, multichannel status and IP-addresses. Maybe it's even possible to list the connected clients with their capabilities (Multichannel, RSS)?!