'Nimbus Sans L' is currently part of
@font-family-sans: 'Helvetica Neue', 'Helvetica', 'Nimbus Sans L', 'Arial', 'Liberation Sans', sans-serif; stack.
It was introduced in rEMFRfe91a50db5b858960f26954aa98b7e036e851374 – but 'Nimbus Sans L' has only been an OS default on early Linux distributions like for example Ubuntu up to 8.10 and was then replaced by 'Liberations Sans'.
'Liberation Sans' should be moved up in the stack before 'Arial'.
Note, the stack is not in use in MinervaNeue any more. But it might be referred to by other consumers of WikimediaUI Base.