If I use the latest standalone version of putty I can connect to this device.
If I try and SSH using the builtin links from Solarwinds or try to do a config backup it fails. I get:

or when trying to backup I see this in the device logs:

A search takes me to some old posts on thwack that suggests the encryption is potentially to new, but the client has had a pen test and it has been recommended they don't use anything less.
The devcies in question are: H3C (aka HPE) MSR2000x series
This, KB Article suggests running a certain command that simply doiesn't exist / work on these devices, but the closest I can find is:
display SSH2 algorithm and then this old (as in 2013 old) post has @lukas.belza saying 'our SSH library is quite old'.
The encryption alhorithm is: aes256-ctr
So, am I out of luck, or is there a trick to get NCM to work?