After downloading broken packages:

    # dnf distro-sync
    [...]
      package firefox-88.0.1-1.fc33.x86_64 does not verify: Payload SHA256 ALT digest: BAD (Expected 9047f23bef8d4d76d2fa672403e178e0ba2aede33df1d110609b9f21fb673977 != c068a24b1ad9c98f60e4fe4172784dec2147154f0f8e6008067d923257d6575f)
      package kernel-debug-debuginfo-5.12.5-200.fc33.x86_64 does not verify: Payload SHA256 ALT digest: BAD (Expected a1eed29ad88ceb61baf5a1daeacabb3c9e86b55efcf5b81b0b5d547eb57f0bcd != fcc2f78645c573200cf5bf171255bab5f854fdbab588ee4b4f3a870d0289039e)

Further attempts fail with the following python trace:

    # dnf distro-sync
    [...]
    Traceback (most recent call last):
       File "/usr/bin/dnf", line 58, in <module>
        main.user_main(sys.argv[1:], exit_code=True)
      File "/usr/lib/python3.9/site-packages/dnf/cli/main.py", line 201, in user_main
        errcode = main(args)
      File "/usr/lib/python3.9/site-packages/dnf/cli/main.py", line 67, in main
        return _main(base, args, cli_class, option_parser_class)
      File "/usr/lib/python3.9/site-packages/dnf/cli/main.py", line 106, in _main
        return cli_run(cli, base)
      File "/usr/lib/python3.9/site-packages/dnf/cli/main.py", line 130, in cli_run
        ret = resolving(cli, base)
      File "/usr/lib/python3.9/site-packages/dnf/cli/main.py", line 176, in resolving
        base.do_transaction(display=displays)
      File "/usr/lib/python3.9/site-packages/dnf/cli/cli.py", line 238, in do_transaction
        self.gpgsigcheck(install_pkgs)
      File "/usr/lib/python3.9/site-packages/dnf/cli/cli.py", line 278, in gpgsigcheck
        result, errmsg = self._sig_check_pkg(po)
      File "/usr/lib/python3.9/site-packages/dnf/base.py", line 1297, in _sig_check_pkg
        sigresult = dnf.rpm.miscutils.checkSig(ts, po.localPkg())
      File "/usr/lib/python3.9/site-packages/dnf/rpm/miscutils.py", line 90, in checkSig
        raise ValueError('Unexpected return value %r from hdr.sprintf when checking signature.' % siginfo)
    ValueError: Unexpected return value 'RSA/SHA256, Wed 19 May 2021 11:27:32 PM CEST, Key ID 49fd77499570ff31' from hdr.sprintf when checking signature.