xloadimage and xmessage are not availble in oracle linux 8_64, at least I could not find em

RHEL 8 has the xorg-x11-apps package in the CodeReady Builder repo which contains xmessage. I know Oracle are a law unto themselves but this might be worth a look at least.

If you just want to view an image in isolation like xloadimage does, then have a look at Gtk3::ImageView.