If the download hurdles are too high, consider:
Each of these is easier to obtain for EVE-NG. juniper vmx download for eveng link
Solution: Enable hardware acceleration.
egrep -c '(vmx|svm)' /proc/cpuinfo # Should be >0
If zero, your hypervisor lacks KVM pass-through. If the download hurdles are too high, consider:
EVE-NG maintains a user-driven database of working images. You will not find direct download links, but you will find hash checksums to verify images you already have. Each of these is easier to obtain for EVE-NG
EVE-NG uses .qcow2 files with specific naming. Copy and rename:
mkdir -p /opt/unetlab/addons/qemu/vmx-20.4R3.8
cd /opt/unetlab/addons/qemu/vmx-20.4R3.8
cp /tmp/vcp-qcow2-20.4R3.8.img virtioa.qcow2
cp /tmp/vfp-qcow2-20.4R3.8.img virtiob.qcow2