Thanks, you saved my day!
Just in case anyone else ends up in my same situation with Neon Live in safe graphics mode stuck in an infinite loop:
On the boot selection grub:
Pick “KDE neon (safe graphics)” and press E key to edit the selection.
On the line: “linux /casper/vmlinuz boot=casper apparmor=0 quiet splash nomodeset ---” add " 3" just after “nomodeset” so it will became: “linux /casper/vmlinuz boot=casper apparmor=0 quiet splash nomodeset 3 ---”.
Then press F10 to boot.
When the login prompt appears log as “neon” and an empty password (just enter).
Then on the command line run:
“startx”
At this point the Neon Live should be back on rails and finally load the desktop.