I have a FW13 AMD 7640u. I have been using an SSD that previously had Fedora installed, with no issues - have never tried to boot from USB before. I now need to redo the disk as a dual-boot with Windows. I have Ventoy installed on a Kingston USB thumb drive. The boot flag is set, and it boots with no issues on several other systems.
What is the status of Secure Boot on your system? This is probably the source of the problem. Why it is the problem will require some digging on your part. But let us know here and the fine folks here in the community will most likely give you a hand.
What’s the error message?