Tracking form submissions in GTM in 2020 Squarespace v7.1

Site URL: https://kinase.co.uk

I want to track form submissions on my site in Google Analytics, I'm using Tag Manager.

I've tried this approach from an old thread (this is direct in Analytics) but it doesn't work. I'm assuming because of the update to 7.1

 Ideally, I'd like to create the trigger in GTM but would be happy with a solution in analytics instead.

I'd like to be able to differentiate between different forms, e.g. when we have a contact form on a page but there's also a newsletter sign-up in the footer I'd like them to be different triggers/goals.

Has anyone advice on how to achieve it?

I'm a fan of this guide. I suspect it'll be solution #3 (AJAX listening). Full disclosure; I haven't tested it on Squarespace.