A good practice for data sources with line breaking issues out of the box, is to get a sample and ingest through the GUI. At least up to the point of creating a sourcetype (you can cancel the ingest after saving the new sourcetype). This allows you to get a preview of the data. The two things you need to get correct when ingesting data is: timestamping and linebreaking. The data preview allows you to see if Splunk is timestamping correctly and if it is linebreaking in the appropriate place.
The data preview also allows you to change settings like those in the post by @harsmarvania57. You can immediately see the effects of the changes and know if you have everything correct. Once the data looks good in the preview, you can save it as a sourcetype, which you would reference in your inputs.conf.
A good tool to help figure out the regex for the LINE_BREAKER is regex101.com.
This isn't an answer, you already have a good one, but hopefully it is helpful information.
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