Create patch or diff file from git repository and apply it to another different git repository

I work on WordPress based project and I want to patch my project at each new release version of WP. For this, I want generate a patch between two commits or tags.

For example, in my repo /www/WP I do this:

$ git patch-format com1..com2 --stdout > '~/patchs/mypatch.patch'

# or

$ git patch-format tag1..tag2 --stdout > '~/patchs/mypatch.patch'

/www/WP git natif WordPress

/www/myproject My git project WordPress based

The git apply command line doesn’t work, I think because we are in different repositories.

Can I generate a patch file without a commit, just a differential and apply it to another git repository?

Thank you.