I don't know if this is going to be fixed; by either Kagi or Mullvad.
Initially I had assumed that this was a simple case of the Mullvad browser refusing to allow Kagi Maps to interpret your location, Kagi Maps not being able to do this constituting an oversight on Kagi's part where the UX was poor because the team had never considered the situation, and it just needing to default somewhere (Palo Alto?) with perhaps a banner message being shown that your location can't be inferred due to privacy / security settings.
Having looked into this, it seems that Mullvad is actually just straight up blocking the Kagi Maps functionality - so your bug report to Kagi would essentially be "Kagi Maps won't work when intentionally blocked", and your bug report to Mullvad would be that their attempts to intentionally restrict browser functionality are successful.
I'm not sure if Mullvad really represents a practical choice for a user's 'daily driver'...
Kagi Maps appears to (perhaps unsurprisingly) use OpenGL, and Mullvad blocks at least some OpenGL functionality - a quick search shows that they, at the very least - block the readPixel function.
Kagi Maps appears to depend upon at least some functionality from mapbox.com, and it wouldn't surprise me if Mullvad was blocking any e.g. third-party cookies with extreme prejudice. Frankly, I'm surprised that Google Maps does work. I can only guess that's down to them being a larger team doing more of the work in-house.
I'm sorry, OP. I think this is a case of "you break it, you buy it."
