Re: memtest86+ seems to do nothing.
I use an old F30 version that's the newest one that works on all my BIOS machines,
namely memtest86+-5.01-25.fc30.x86_64.rpm. It's in the archive at
https://dl.fedoraproject.org/pub/archive/fedora/linux/releases/30/Everyth...
. Adjust the path if you need a different arch. I only run it once every couple months. I
install the RPM via command line, run memtest-setup, grub2-mkconfig -o
/boot/grub2/grub.cfg (the command that memtest-setup tells you to run), reboot and run
memtest+, then remove the package when done (otherwise dnf will want to update to a newer,
nonworking version). Just keeping that RPM around and installing/running/uninstalling
every few months is easy enough for me.
If you want to verify the RPM, then import the F30 key which should be available on your
machine at /etc/pki/rpm-gpg/RPM-GPG-KEY-fedora-30-primary.