My hardware is incompatible with the default installer that comes with Manjaro live media. In fact, all distros' bootloaders fail on it when run from USB. Is it possible to change the default bootloader? Machine uses UEFI but apparently has CSM. Thanks!
Can you be more specific? For example, what do you use to create usb media, which options you choose on Rufus, say. Did you try to disable CSM and use UEFI instead (preferred for any OS if available).
I tried lots of image burners, including Rufus, Etcher, dd, GNOME disk image writer and UNetbootin. I wrote the image both in ISO and DD mode, to no avail. The boot menu appears and I can set some startup options, but then if I choose to start the live OS, the bootloader freezes without any further output. I read this, which states that sometimes GRUB can't access USB devices due to BIOS limitations. Since the same live media boots flawlessly on another computer in both BIOS and UEFI mode, but not on the target machine, I'm certainly sure it is a firmware issue.
Well - then it seems the firmware on the target system does not support booting from an USB media.
Either update the firmware on said system or .... imagine other options for yourself
What about the GRUB2 command-line? Like, I could use 'linux' to load the kernel, then 'initrd' to load the ramdisk, and finally 'boot'.
If your question is
how do I use an existing bootloader on the system using my usb key
You could use the forum search function and locate posts by @gohlip narrowing the search using keywords like grub edit
32 bit uefi?
Acer Aspire E15 E5-573G?