alt Hacker NewsI don't know how much of that 6 hours build is tangled up in github workflows, but if it's a single contiguous block, you probably could make it near zero by making the self-hosted runner do only the preparation and only the final upload process (workflow_dispatch when the build is complete).
Most of it is just time waiting either while the source assets are downloaded (I clean slate it, that's the point of CI after all), the build itself runs, or the artifact is uploading to it's storage home. I'm sure it could be re-architected to use less actions minutes but if I'm going to redo it I will probably just move away from actions altogether because it's only loosely linked to Github anyway (runs on a schedule) and that way I am insulated from any future changes they come up with. The hardest part will likely be figuring out the Slack bot posting, I do use the marketplace action for that, but that's probably low lift. With LLM assisted coding I'm leaning more and more to little in house apps for stuff like this, it keeps you from dealing with lock in and other extractive gotchas.