NMSSNM0075 Username must be less than or equal to 8 characters.
when running one of these commands in Gaia Clish, although USM user with longer username was created successfully with "add snmp usm user USERNAME" command:
set snmp usm user USERNAME usm-read-write
set snmp usm user USERNAME usm-read-only
In WebUI the acceptable USM username: "Username cannot exceed 31 characters.":