And is it going well?
A qualified "yes".
Dependabot has ~100 paying customers, and makes just over $2,000 a month. It's still quite a lot of work adding new features, but if I wasn't extending it's functionality it would be passive income.
Personably have raised money and landed some big paying customers - I think there's scope for them to be solving a relatively large problem, having started from a duct-tape fix.
The only proviso I'd add to the article is that sometimes the problems you find like this are small. Dependabot will never be a full-blown startup - it's scope is too small. That's not necessarily a bad thing, though - I think the problem has still been well worth solving thoroughly.
Don't any of the langauges you support have options to keep all dependencies up to date? Eg. By putting wildcards in version numbers
That’s normally an option for your manifest file (e.g., a Gemfile or package.json), but most production applications also (sensibly) use a lockfile. Updating the versions in that lockfile is what Dependabot is great for.
Another group of friends started Personably from exactly the same strategy - we had a script to create dozens of calendar invites for new joiners with all their onboarding details, so things didn't get missed.