I did some research on this. The failure is due to the Chromium version being too low. OpenLP is using an embedded version of Chromium which is contained in the QT WebEngine libraries.
OpenLP 3.0.2 is using QT 5.15.2 which has Chromium version 83.0.4103.122 embedded. To fix this, OpenLP will need to be updated to use QT 5.15.11 or higher which has Chromium 87.0.4280.
I figured this out by reproducing the issue in a full version of Chrome. I used the developer tools to spoof an older version. This reliably produces the same error message as seen in OpenLP when logging into Song Select.