Monorepo just didn't work for me. I have ~10 web projects for different customers + my personal projects that use various versions of some common code.

It doesn't make any financial sense to evolve my common code by updating all the customer's code for free when they're not even asking for it. So on this level it doesn't work.

Even within a single company with just two devs and around 90 repos for the main product and plugins, it was hard to justify making a mono-repo with plain git, because plugins and the main app had different release schedules, priorities, so it never really happened that it was economical to port all plugins right away to the new version of the main app on every change.

I still think going multi vs mono is a business decision, rather than a technical one. You'll have to have special tooling for either case, just a different one.