Create Install Media El Capitan

Am I correct in assuming that it's not possible to create bootable USB install media for El Capitan using an ARM-based MacBook (Big Sur)?
My brother-in-law brought me a Mac to fix, it looks like the OS was wiped or corrupted and the recovery partition was useless. It had El Capitan, but I've not been able to create a usable bootable USB using the DMG from Apple's site. I've tried with my M1 MacBook, I've tried using TransMac on Windows, but that didn't seem to help (wasn't bootable). I'm at the point where I'm thinking I need to tell him I'll have to purchase the physical media because the recovery mode won't even let me download the OS, I assume because you need an iCloud account with the OS tied to it. I can't believe how needlessly complicated this is (or I'm making it?). /whine
CapitanCreate

Create Install Media El Capitan Installer

El Capitan:. If your Mac is using macOS Sierra or earlier, include the -applicationpath argument and installer path, similar to the way this is done in the command for El Capitan. Osx Create Install Media El Capitan. After typing the command: Press Return to enter the command. When prompted, type your administrator password and press Return. How to create an El Capitan USB install disk Step 1: Download El Capitan from the Mac App Store. If you’re a developer, you can redeem a download code to use via the Apple developer center. If you’re a part of Apple’s public beta program, you can likewise redeem a code for the El Capitan GM via Apple’s beta website.