Recent Update shows slow Android Performance

Unity Engine
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1

I recently updated from unity 2018.2 to 2019.2.

Besides updating some plugins, removing google admob and downgrading to JDK 8 (from JDK 9/10) the code is mostly the same.
I noticed that my app is significantly slower during scene loadings. It was much faster in the previous version (pre-downgrade to JDK8 and Unity 2018)
The slowdown is only on Android devices. For desktop and iOS devices it is still as fast. Even an old iPhone5 has better load times than more modern Android devices after the patch.

Would anyone have any suggestions on how to debug/look for the cause of the issue?
On loading the scene, the app instantiates a good number of objects. (I know its not the best format and something I will rewrite eventually) - I assume that the loading lag is tied to this.

Some thoughts:
Could downgrading the JDK be causing the slowdown?
Could the app be reaching the OS memory limit and thus causing the slowdown?
Would anyone know if there were some changes that could cause a slowdown/change in processing for Android devices?
Android resolver complains about missing artefacts and exploded files but seems to run okay.

2

Are you building an AAB and do you have asset bundles in the StreamingAssets?

3

Yes the app is built with AAB in both cases. I don’t use streamingAssets but most of the resources are placed outside of the resource folder save for some small image files. The app makes plenty of usage of files in persistentDataPath though and most of the content is player generated.