

Just being open source is not enough to solve this problem. You would need a record of your “home instance” stored somewhere that all Lemmy instances would always have access to it. Ignoring the security implications of that, you still can’t use browser storage or cookies for that storage. In browsers, those storage mechanisms are restricted to the websites that stored them in the first place. Browser extensions have their own storage, so they don’t have this limitation.
I can’t think of an architectural solution to this problem without a browser extension.
The closest alternative that could be upstreamed is what Mastodon does, which is prompt the user to enter their home instance every time they try to interact with something while not logged in. An upstream solution can never be fully automatic like a browser extension, but this may be “close enough.”
The people downvoting you have never experienced perfectly regular trees (and don’t understand CrossCode inside jokes).