ARM64 has a number of differences in the calling convention, prologues, and epilogues that cause ROP to be different than on x86_64.
Because these challenges are running on an x86-64 host, you might need any of the aarch64-linux-gnu-* tools, such as aarch64-linux-gnu-objdump.
gdb is now a 2-step process:
In one terminal / tmux window:
$ /usr/bin/qemu-aarch64-static -g 1234 /challenge/level-1-0
In another:
$ gdb-multiarch /challenge/level-1-0
(gdb) target remote localhost:1234