Hi there,
GIF featured images should work for the post thumbnails on the front page grid, yes. I tried it out on my test site with GIFs of various sizes, and the front page showed them all without any problem.
As an aside ive noticed it hasnt been updated since 2018 – is this likely to be a problem in the future?
Not in the immediate future, but as WordPress continues evolving, the theme will eventually become incompatible and stop working.
We launched this theme in 2016, so in web years it’s already quite old. The theme also predates the block editor. Our current focus on themes at Automattic is on creating themes that will work with the full-site editing features that are coming in WordPress 5.9, so it’s very unlikely that we’ll make further updates to this theme aside from critical security fixes, and it’s also not likely to be prioritised in terms of bug fixes.
You should be able to still use the theme for at least the next few years, though. Also keep in mind that what I said above about the theme eventually becoming incompatible is true about any theme…no matter what theme you choose, you won’t be able to use that theme forever, as any theme eventually reaches a point where it’s no longer feasible to continue maintaining it, at which point the theme developers will rather retire it.
if so can anyone recommend any very similar wordpress themes (preferably free)?
I’m not able to recommend any specific themes, but you can see all themes in the theme showcase that offer a grid layout using the filters in the showcase:
https://www.ads-software.com/themes/tags/grid-layout/
The ability to organise contents based on categories is a core feature of WordPress itself, and doesn’t depend on what theme you’re using.