[Amazon OpenSearch Service] Is custom plugin upload supported for OpenSearch_3.5 engine version?

Versions: Amazon OpenSearch Service, OpenSearch 3.5, AWS console (web interface, not cli)

Describe the issue: I’m working on custom plugin, have uploaded it to S3 bucket. When uploading it as a plugin, it keeps failing on validation step.

I read the documentation about developing custom 3rd party plugins. But the logic for AWS’s custom plugin validation for OpenSearch Service is still a mystery for me.

What I tried so far in 3 distinct tries:

What we set Validation error response
opensearch.version=3.5.0 “not supported for the provided engine version”
dependencies=^3.0.0 (no version) “missing mandatory: opensearch.version
opensearch.version=2.17.0 “doesn’t match provided engine version OpenSearch_3.5”

Any ideas or suggestions?