starts fading out OscryptoDownloader by disabling it on python 3.8 (aka ST4) platforms.
fixes original logic to disable OscryptoDownloader for ST3 on linux.
Reasons:
OscryptoDownloader relies on oscrypto which hasn't seen any viable updates for about 2 years at the time of writing this.
MacOS related CI tests for python 3.8 start failing as Github Actions moved to ARM platform. The downloader just gets stuck without any error messages.
caused by #1676
This PR ...
Reasons: