From the post at The Federalist:
The guidelines state: “if [a business or organization] offers some services, facilities, or goods to the
general public, it will be treated as a public accommodation”
The thinking here follows the rationale in the HHS mandate promulgated a few years ago by the current administration under the Affordable Care Act, which essentially asserted that an organization doesn't have the enumerated free exercise rights of a religious organization if it serves the public. The HHS mandate seemed to make an exception for a public worship service. The so-called Iowa Civil Rights Commission seems not to. Of course, Vacation Bible School, Sunday School, a food pantry operated by a congregation, allowing the congregations facilities to be used by a 4-H group, Cub Scouts, or for a Red Cross blood drive all would seem to run afoul of the regulations if non-members are served.
Note well that the guideline says, "offers some services." Any of these things offered to the general public causes the organization to be treated as a public accommodation even if it's only a small part of the organization's activities. And as a public accommodation, no free exercise rights remain.