Convert map output from module to list to use in other module

I managed to use for_each to create resources in regions based on a given array. Now I want to use the output URNs to assign the resources to a project in Digital Ocean. The problem is that the way I output the URNs for the resources creates a map while the project_resources resource can only use lists of strings.
My code:

output "droplet_urns" {
  value = tomap({
    for k, drops in digitalocean_droplet.web : k => drops.urn

How can I convert the map into a list or use the value based on the key? I’m using Terraform v1.1.9