Often if people call and ask how to find a support group, we suggest they call the social worker at the area hospital. Often these are run out of there. We also suggest calling the local health agency that deals with your loved ones condition. They may have or be wiling to start a support group. There are online chats.
Resources depend on the specifics.
The elder care locator can help you find out about resources for seniors in your area. It can point you to the area agency on aging in your area. You can check with county offices on senior services or elder affairs. Family Voices is an organization that is helpful. It's an advocacy organization.