I know I can create a list template and share it at the site collection level (from the gallery). But is it possible to share a list template across all site collections in a tenant? Similar to what the App Catalog does with add-ins?
Maybe try to use a migration tool like Metalogix or Sharegate to deploy the template across the site collection. It's not exactly a solution, more of a workaround, but it should do the trick.
After you save a list as template, it will be saved in List Template Gallery. You can download the template from the List Template Gallery, then upload it to other site collection's List Template Gallery, then you can create the list from other site collections.