Medicaid is a state program and one needs to qualify under the state rules. There are still some states that did not expand medicaid so adults may not be included. 13M people were just dropped from medicaid because the federal program that extended benefits because of covid expired, with very little notice. Some states have income requirements so low that earning minimum wage can make you ineligible. I think in Colorado the single person max income is about $14k to qualify, and with minimum wage in Denver @$18.29 as of Monday, 40 hours per week would be $38k; even 20 hours/wk is $19k. There were articles last week about the millions (3 or 4M) of Texans who were just dropped from medicaid.
Options? ACA programs in the state of residence
Cobra if the parents’ plan is covered (can be $500-$1000/mo)
Employer’s (child’s) plan
Just before Christmas I got some ads on FB about programs with enrollment dates of 12/15 or 1/15, but usually you can enroll in those plans if there is a change in your coverage. One was healthcare.gov