What are options for dependents 26 or younger if they lose their health plan?

You may cover. They may be added to your plan up to age 26.
You go get another. Emancipated minors and individuals can seek out and find health care coverage. They may not like the price tag, since most plans now require stuff you never need, like baby care and contraception for 55 yo grandmothers, but there are plans out there.