Hi,
By default, local.conf does not exist. You need to create local.conf file by yourself for manual configurations such as multipath. Manual configuration can be achieved by creating the file local.conf in the program's home directory /var/lib/zerotier-one. This allows you to set various configuration options, such as restricting the service to specific interfaces or enforcing the use of a different port. This file must be valid JSON as it can be re-written by zerotier-one.
Please follow the link below for more information:
https://wiki.archlinux.org/title/ZeroTier#Manual_configuration
Regards,
Ramandeep