OpenSCAD is, I believe, a 32 bit app. The results of your “whatprovides” query show the package as an i686 (32 bit) package.
All your searches show that you have the so file but if you look at the location in your whereis query you see it in the /usr/lib64 directory which is 64 bit libraries. Your system also shows as 64 bit in the uname output.
I found this using a dnf query
#dnf list qt5-qtbase
qt5-qtbase.x86_64 5.14.2-5.fc32 @updates
qt5-qtbase.i686 5.14.2-5.fc32 updates
Notice there are both 32 and 64 bit versions of the qt5-qtbase package available. I suspect that if you install the 32 bit package alongside the existing 64 bit package it will solve your issue.
I am currently running f32 but I suspect the packages are similarly available.
As far as I can tell, openscadis a 64bit application:
$ dnf search openscad
Last metadata expiration check: 0:24:23 ago on Sat 15 Aug 2020 05:55:04 PM CEST.
============================================ Name Exactly Matched: openscad ============================================
openscad.x86_64 : The Programmers Solid 3D CAD Modeller
$ file $(which openscad)
/usr/bin/openscad: ELF 64-bit LSB pie executable, x86-64, version 1 (GNU/Linux), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, BuildID[sha1]=0554686e641055a103bf148644d6c058ded7aae2, for GNU/Linux 3.2.0, stripped, too many notes (256)
On another hand, the requested library (“libQt5Core.so”) is not installed with the 64bit version of the package “qt5-qtbase”, but is well installed with the 32bit version of the package.
(Checked by force removing both versions of the package, and re-installing one by one.)