This causes a deprecation warning on all subsequent uses of Portage:
/usr/lib/python3.11/site-packages/portage/package/ebuild/_config/KeywordsManager.py:86: UserWarning: /etc/portage/package.keywords is deprecated, use /etc/portage/package.accept_keywords instead
This warning must be resolved by manually moving the file into the `packages.accept_keywords` directory.
When autounmask is next used, the file is freshly created in `packages.keywords`, and you have to manually merge the old and new `zz_autounmask` files.
A fix for this would be to simply have Portage create the `zz_autounmask` file in the `packages.accept_keywords` directory instead.
My Portage version is 220.127.116.11
Did you already have a package.keywords directory?
Not unless it's created by default, this was a fresh install