The only way I can see a federated system like this to open links reliably and constantly would be to avoid dealing with hostnames, and instead define a protocol handler.

Similar to how email client works. You email client is set-up with your mail provider, and the OS will handle the protocol and pass that info to the client

ie: mailto:username@example.com?subject=Hello&body=Test will make your email client make a new email to be sent to username@example.com, with the Title Hello and Test as the email’s body.

Something for Lemmy could be make such as lemmy://!lemmyconnect@lemmy.ca to make you open that community in the Lemmy app of your choice. The syntax and parameters could be different than what email defines, I’m just setting an example. Parameters could be made to send a DM to another user, set up filters, sort order, etc.

Using a protocol handler would make home instance irrelevant and redirections wouldn’t be necessary, as the client/app would do all the heavy lifting.