Working with WordPress multisites in Local can be tricky, especially if you are importing an existing network. Because there’s often some adjustments that need to be made to the various server configs, it’s usually better to create a multisite in Local from the beginning.
Can you try creating a new, plain multisite? Follow the usual process, but on the third step, select the type of multisite you want to use under “Advanced.”
One thing to note – since you are using the localhost Router Mode, I think you can only use the “subdirectory” option and not the “subdomain” option.