In order to install GNOME Tweak Tool in RHEL 8, first we need to enable rhel-8-for-x86_64-appstream-rpms repo

subscription-manager repos --enable=rhel-8-for-x86_64-appstream-rpms

After enabling repo, execute following command:

sudo dnf install gnome-tweaks

Enter y to confirm

Gnome tweak tool is installed

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