IRS just announced in IR-2023-23 that the MCTR is not federally taxable:

"The IRS has determined that in the interest of sound tax administration and other factors, taxpayers in many states will not need to report these payments on their 2022 tax returns.
During a review, the IRS determined it will not challenge the taxability of payments related to general welfare and disaster relief. This means that people in the following states do not need to report these state payments on their 2022 tax return: California, Colorado, Connecticut, Delaware, Florida, Hawaii, Idaho, Illinois, Indiana, Maine, New Jersey, New Mexico, New York, Oregon, Pennsylvania and Rhode Island. Alaska is in this group as well, but please see below for more nuanced information."