Do you have any ideas for a password safe that stores its data locally (an encrypted cloud drive is available for synchronizing), offers clients for Linux, Win and Android and has some amenities like filling in passwords in browsers?
My family needs to learn password safety, and I want to make it easy for them.
Bitwarden, Bitwarden, Bitwarden. Use their free vendor-hosted service, and don't fixate on self hosting or handling syncing of local files. They are highly transparent and well regarded, and this is the way to go if you want any hope of converting your family.