I have two laptops, both working. I need to make a clone of one in other, without removing and of the HDDs (warranty)
Is it possible using CloneZilla or any other software?
I can have both machines running Ubuntu Live USB if needed.
Yes, this can be done (but may only work if the laptops are very similar hardware wise, or if you have drivers for both in the OS). One way to do this would be to USB boot both laptops, run an SSH server on one and ensure it allows root access - then pipe cat (or pv - which requires an apt install pv)I over to read blocks from one and write to the other. Once ssh as root and pv is set up, a command like
pv /dev/sda | ssh x.x.x.x "cat > /dev/sda"
should work - but make sure understand how this works so you don't stuff something up.