For moderator support you need to post in the CMS/Template specific member only forum... ie "Joomla - Studius".
What forum can I move this to?
If you're new to Gantry powered themes I highly recommend you take the time to read the first six chapters here (Particularly the Layout Manager):
docs.gantry.org/gantry5/configure
.... and search/consult the docs as needed as there's quite a bit there.
There is no "sticky footer" concept in Gantry or Gantry templates. Gantry is very flexible and allows you add classes to any sections (rows) or blocks (particles) along with the ability to set inline style attributes (or other attributes) on all the grid framework elements.
Gantry uses Flexbox for its grid system so you could try something like:
css-tricks.com/couple-takes-sticky-footer/#aa-there-is-flexbox
-- but ultimately the custom dev would be up to you, so if you're not familiar with CSS you would need to consult with a developer.
From a best-practices standpoint I would recommend ensuring that you're rendering content on every page that at least fills a 1000px vertical area.
Depending on what theme you're using you can use the built in Variations available on each Section (rows) as well as each Particle/Block to add "Veritical Paddings" and Top/Bottom Margin and Paddings to help create some of that space.
SEARCH the forum first! These boards are rich in knowledge and vast in topics. This includes searching just the 'Solved' forums, using Google, and using ChatGPT