Thanks @Sumarigo-MSFT for your feedback. It is for logs produced for a java app running on IaaS. I have received feedback through another channel which looks to be what we are after:
"As I understand, you want to upload some log file from a 3rd party solution to log analytics.
I suggest you try custom log:
Collect custom logs with Log Analytics agent in Azure Monitor - Azure Monitor | Microsoft Learn
This requires you:
You can login to the console of the netapp and deploy OMS agent.
The index file you mount, it can be accessed by file system.
The index file’s formant is supported by custom log."