boot – Error: file /casper/vmlinuz not found, you have to load kernel first

I’m trying to install Regolith version of Ubuntu and. I’ve put iso installation file on USB via Rufus, but when I booted with that, it wrote that file /casper/vmlinuz not found and I have to load kernel first.
I tried to redowload the iso file, check existency of /casper/vmlinuz or if there is vmlinuz.efi, tried 2 different USB sticks, both BIOS and UEFI type of iso, but nothing works.
Can somebody help me how to solve my problem?
Thanks in advance.