As of 2020-08-01, You can't install scilab via dnf/yum.
Can't install scilab - Discussions in English / on using Fedora - Ask Fedora
In order to use scilab, you can download tar ball from official web site.
Still you can't start scilab because of a shared library error.
1829790 – libk5crypto.so.3: undefined symbol: EVP_KDF_ctrl, version OPENSSL_1_1_1b
You can use scilab after renaming /your/path/to/scilab-x.x.x/lib/thirdparty/libcrypto.so.1.1 to random name.