default Dolphin Preview behavior changed; looking for setting to change it back

[Bug Reporter]

Generally, I do not keep Preview enabled for most of my folders. After this
recent update (18.04.0), Previews are now enabled by default for all
folders. I wish to return to the prior behavior.

I'm running KDE on Arch.  Here's some system info:

    plasmashell --version: plasmashell 5.12.5
    dolphin --version: dolphin 18.04.0
    Linux 4.16.6-1-ARCH #1 SMP PREEMPT Mon Apr 30 12:30:03 UTC 2018 x86_64
GNU/Linux

Is this recent change related to the following bug?
Bug 338492 "File icon previews should be turned on for all icon types by
default"
https://bugs.kde.org/show_bug.cgi?id=338492

I personally disagree that file icon previews should be turned on for all
icon types by default.

However, if that is the new Dolphin default, I hope there is a setting in
Dolphin (or a config file) that will let me revert to the prior default. If
so, where do I find it?

Any additional information about this change is appreciated.
I filed a bug report here: https://bugs.kde.org/show_bug.cgi?id=393978

Thanks
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