Further information thanks to our first volunteer helping:
We need logs with the code that talks to the eUICC (ApduSender, SIM_OPEN_CHANNEL, etc.).
We will need both, the logs from SIM Manager and the system log with radio buffer.
Submit a system log with just the radio buffer enabled together with logs from SIM Manager (com.google.android.euicc).
How to collect the logs:
System Log:
Found under Settings -> System -> View logs -> Log Buffers -> Radio
SIM Manager Log:
Found under Settings -> Apps -> Show all -> 3 Dot Show System -> SIM Manager -> View Logs
There is actually a "Show system log" button at the bottom when viewing SIM Manager logs that can be used after SIM Manager logs are saved which will be easier.
Both of them should be submitted immediately after an eSIM activation attempt so that the radio buffer logs can be lined up the events in EuiccGoogle.