Have you considered using a client-side solution like the Requestly browser extension for Google Chrome? I just tested this with a rule to match inaturalist.ca in the host and replace it with inaturalist.org, and it works. It may not be an ideal solution, but it’s better than nothing.
In our iNaturalist Discord community, people often cut-and-paste observation URLs from their own affiliate sites into chat channels, and then I have the same problem: I have to either manually change the URL, or else login to their site in order to interact with the observation. This use case is similar, but wouldn’t be addressed by this feature request. The Requestly extension, however, handles both cases.
Ultimately, for myself, I decided that it caused the least hassle when sharing my stuff to just switch my affiliation from .ca to .org and it has remained that way ever since.