I've had a poke around with AssetRipper and DNSpy and am pretty sure that AES keys are used in some fashion.  The StreamingAssets folder files are all missing their proper UnityFS headers, and instead have jumbled characters where those should be.  I've attached ten files here in hopes that either they all use the same key (unlikely) or that someone can point me in the right general direction of how to decrypt them in general since the file structures seem relatively intact.

eo.zip

You were right about AES and the broken headers. The game builds a different key for each bundle from its filename and a fixed password, then scrambles the first 128 bytes. The rest of the file is left alone.

I put together an article covering everything I found.

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Use the script as follows:

# Single file
python .\etrange_bundle_decrypt.py ".\encrypted.bundle" ".\decrypted.bundle"

# Entire directory
python .\etrange_bundle_decrypt.py ".\Master" ".\Master_decrypted"

etrange_bundle_decrypt.py

Edited September 4Sep 4 by Falkrian