Hello Nick, its nice to have you here, too!
At first: A huge thanks for the effort you put into this. I am really touched by the amount of work you spend into this and especially by your kind words about me and the community. Wow!
I think there might be some confusion, maybe its just something I get wrong. So lets try to make this clear to avoid any confusion.
At first: The “For everyone across all instances” option is only visible for everyone out there without being logged into any Funkwhale instance if your instance allows anonymous access to its API. This is true for open.audio, but might not be true for some other servers. In this case their “For everyone access all instances” means basically everyone who is logged in to any arbitrary funkwhale instance is able to consume the activity feed via the federation.
Secondly, the ticket you linked is probably not exactly what you want. Because the ticket is about federating the activity feed, eg by sending the activities to followers on other instances. This still does not mean this content would be public, its only visible for users on other instances if they follow you.
The good news is, though, that the thing you want to achieve is remarkably easier to implement. Its probably really only one settings and a little bit changed queryset and we are ready to do this. I’d need to investigate this, though, so no promise here.
About your more general question how to get your feature request into Funkwhale. At first I really appreciate you are asking for this and starting the discussion. Its much better to go this way than simply complaining your favorite thing is not available. So thank you for this attitude!
The question is quite big and maybe hard to answer. The huge, basic issue is that we have way much more feature requests and ideas to work on than we have the developers time to implement it. We could probably close our issue tracker and work for 10 years and I am not sure if we would even get everything done. Additionally there is a lot of work to be done due to, lets call it technical debt. This means we need to change our code to reflect changes in libraries we rely on, find and fix bugs or search for other solutions for something which does not work well at scale. Additionally to all this we have a lot more tasks to work on, which are not related to coding. We want to stay in touch with our community, we want to be more inclusive, we want to work on networking and connectivity with other fediverse software, we have the idea to do some content curation and improve options for artists and creators to earn some money with their free content.
To sum this up: Yes, we have a huge discrepancy between ideas and resources to work on. So we need to prioritize, which was done by a community voting in the past and is somehow done with a funding we have (which nobody uses at the moment, though). So in the end, there is no easy way to solve it. I think what you really want to have is nothing we need to have a huge voting about, but we need somebody who work on it. And this, again, is not really easy to solve, even if you would throw money on a developer, we would probably work on other stuff, too, anyway, because we think we need to fix some pretty basic features, first.
For me personally I could consider working more on Funkwhale if there would be a funding which allows me to quit my job and still leave the freedom to work on what the Community or the dev teams says is useful. But I am quite critical about bounties.
This is just a dump of my thoughts and probably does not reflect the position of the Funkwhale dev team or community. And this discussion probably needs some more space and should be done besides the discussion of your feature request.