Hi @txiong
Thank you for update.
It's still impossible using variable. Because we can't find all lists using one action. Even though we can put list details in variable, we still need to use 'get items' for each list as we can't input dynamic value in site address and list name.

Thus, we can't achieve it using flow. That's why I try to find other methods as workaround for you.
Sorry for the inconvenience may caused. Hope its clear to you.
Thanks
Anna