The Creative Commons license explicitly states that it’s not meant for software.

My personal recommendation for a good public domain license is the 0BSD-license, which is the ISC-license (which again is a reduced MIT-license) with the attribution clause removed. I would always state the license name at the top and, unlike OSI, explictly mention the copyright:

0BSD-License

Copyright 2010-2022 John Doe <john@doe.com>

Permission to use, copy, modify, and/or distribute this software
for any purpose with or without fee is hereby granted.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL
WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL
THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR
CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING
FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF
CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

I think that it elegantly solves the problem that there are still many jurisdictions that don’t have the concept of a public domain. Instead, you remain the copyright holder and claim the copyright, but don’t impose the rule that you’re attributed for this in any form. The license is also extremely simple.

If you want attribution, use the ISC-license instead, which has a slightly different clause:

Permission to use, copy, modify, and/or distribute this software
for any purpose with or without fee is hereby granted, provided
that the above copyright notice and this permission notice appear
in all copies.