It may not be possible to find error logs for previous boot failures since the liveUSB doesn’t have persistence by default: [root tip] [How To] Multi ISO USB with storage partition
Have you tried using a Minimal LTS ISO (available from the same download page) ? I believe it ships with the 5.10 LTS kernel.
Do you launch the liveUSB with the free or non-free GPU driver?
FYI, those commands are for diagnosing issues on an installed Manjaro, which is then not the present case.