It would be cool to pay a monthly subscription, that’s then distributed among the software I use or have installed. That could be integrated into a package manager even. I don’t know if any Linux distro does something like it.

I've been thinking the same thing lately. It would be cool if at least there were some sort of metadata maintainers could include on packages saying, "if you want to donate money, upstream accepts donations at this link: <...>". Then I (or someone else) could put together a tool that helps you track what upstream projects you're donating to.

I understand that isn't nearly as easy as just a subscription though. The issue I see with that is legal - you'd need a legal entity specifically for accepting payments and disbursing each upstream project's share, plus all the accounting and such that goes along with it. I don't see why it couldn't be shared across multiple distributions though. Upstream packages could create an account with the funding service, then distro maintainers could include some sort of Funding-Service-ID: gnu/coreutils metadata and a way to upload a list of Funding-Service-IDs to the funding service's servers.

I think that would be doable, but it would require buy-in from distributions, upstream maintainers, and someone who could operate such an organization. Not to mention users.