mfix-22.1 has been superseded by mfix-22.1.1 which was a bugfix release - when we make bugfix releases, they obsolete previous version - there is really no reason to run 22.1 instead of 22.1.1 because they are identical except for a few fixed bugs.
However if you really need an obsolete version, you can just modify the download command:
conda create -n mfix-22.1.1 mfix==22.1.1 mfix-doc==22.1.1 mfix-gui==22.1.1 mfix-solver==22.1.1 mfix-src==22.1.1 -c conda-forge -c https://mfix.netl.doe.gov/s3/...
just copy the command from the website, and change all of the instances of mfix-22.1.1 to mfix-22.1 (6 places, make sure you get them all)