Health interventions are tough, and they kinda go on forever. I wonder if this kind of work could be best approached as a community health project, like a community clinic type thing. Rather than focusing on getting people to adopt covid protocols, focus on getting people involved in addressing the healthcare needs of marginalized and disabled people in the community. That way you're pulling people into a context where they're asking for training to be able to safely assist their neighbors and struggling together to improve health outcomes in the community. This might not be exactly the focus you're looking for, but I think there's a broader issue that forms the backdrop of the general apathy towards covid safety. I bet there are multiple mutual aid groups in your area who would be open to expanding their services to include basic health training and care.