Can't authenticate Fitbit integration

Configuration
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I’ve been trying to setup the Fitbit integration and it’s not going so well… here’s my config.yaml:

  - platform: fitbit
    clock_format: 12H
    unit_system: metric
    monitored_resources:
        - "activities/activityCalories"
        - "many more activities"

My callback url in the Fitbit dev app is https://192.168.1.141:8123/api/fitbit/callback . I followed the first part of the configuration; I added my client ID and secret to the fitbit .conf file and restarted my HA RPI.
Now in the notifications I see a popup saying ‘please authorize Fitbit by visiting http://192.168.1.141:8123/api/fitbit’. If I do that, it gives me the ‘app provided invalid information’ error; however, if I change the redirect_uri in the url to https instead of http, I get the Fitbit permission page. Enable all permissions, then hit ‘allow’, and I get a weird page saying ‘This site cannot provide a secure connection’, since it’s trying to get to https://192.168.1.141:8123/api/fitbit/callback?code=xyz&state=abc. I remove the s to make it http instead and it gives me a 500 error with ‘server got itself into trouble’. I have no external IP for this HA RPI (as far as I know; I’ve used it purely as an internal thing so far), so how do I get the callback URL to be correct?

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