I had the same need and also cobbled something together to do it. This project looks far easier to use, so I will also likely switch. Checking the Dockerfile t

I had the same need and also cobbled something together to do it. This project looks far easier to use, so I will also likely switch. Checking the Dockerfile this also uses qemu to run the actual ARM binaries, I really liked how easy it was to set this up back then. All I had to do was loop mount the RPi image and then chroot into it. Everything else was handled transparently by qemu. Of course, I didn't have nice things like resize, so I was limited to making small additions.