I’ve been working on an open source project called Pando (https://github.com/trypando/pando) that is meant to help with part of this problem. Specifically the last part of your question, which inventories these apps.

When someone at a company builds an app, they become the owner/maintainer of that app, and it can be transferred to someone else when leaving, or to a group/team for shared ownership. Or, it can just be decommissioned.

I think it’s important to treat internal tools built by non-technical employees essentially as drive data. It should be shared with those who need it, and if it needs to be kept forever, it should be owned by a group or “shared drive”.

With that said, I also think that as a developer building internal tools, you fall into a bit of a different bucket. When contracting with these companies, I imagine the expectation is that you will build something high quality and maintainable, which can be passed off to a platform team. This is functionally different from non-technical users building their own tools.