At least as of August 2022, the IRS was still issuing paper bonds. The IRS has provided the following with regard to bonds in certificate form:
10. Will I get actual paper bond certificates?
Yes. Savings bonds purchased with a tax refund will be issued as paper bond certificates in your name. If you are married and filed a joint return, the savings bonds will be issued in your name and your spouse's name. If you purchase savings bonds for someone else, the bonds will be issued in the name(s) that you listed on Form 8888.
Here is a link to IRS information regarding using a refund to buy a U.S. Savings bond.