"unable to contact server" error on self hosted CHT

[mrjones-plip]

On a Samsung A71 or Sumsung A30 running Android 10, we can not access our CHT instance running in Docker. Using the unbranded app, we get a “unable to contact server” error.
Steps to reproduce:

1. Install the CHT using docker-compose and a local only DNS entry and *.my.local-ip.co TLS certs per this forum post. This result in cht.my.local-ip.co being the URL for a CHT instance with a valid TLS certificate.
2. Using a Samsung A71 or Sumsung A30 phone, download the unbranded 0.8.0 Android app from the Play Store
3. Connect to the LAN where the CHT is hosted
4. In the app, enter the URL https://cht.my.local-ip.co

Expected: The app connects to the CHT instace
Actual: The app shows a “unable to contact server” error and doesn’t connect
Related: Going to https://cht.my.local-ip.co in a browser on either phone works. Going to https://cht.my.local-ip.co on a desktop on the same LAN works. Using the test instance https://gamma.dev.medicmobile.org in the app and the phones’ browser works.