Overcoming softlock when creating /system/xbin on Android 9

Hoo roo, Installing Linux Deploy (Linux chroot with root) on Android 9 requires that you install a custom version of busybox . However, due to system-as-root limitations on Android 9, you can encounter problems when attempting to run the custom busybox installer. The community has found a solution to overcome this , but I can't seem to get it to work. My tablet is a rooted Onyx Boox Max 3 that has TWRP installed without a custom ROM, with dm-verity disabled. Running

-l which su

from a terminal emulator returns

1 root root 8 1970-02-11 19:10 /sbin/su -> ./magisk

so confirms that I am using the root busybox.

/system/xbin

after mounting /system as per instructions softlocks the tablet. Have also tried running

-o rw,remount /sbin/magisk/mirror/system_root

which also softlocks. Are there any other options that I can try? Would really love a chroot of Arch on my eink tablet instead of just a proot. Would make for a much smoother experience. Cannot emphasise how desperate I am, my failsafe is a proot using nix-on-droid, but reckon that performance will suffer. Does anyone have any ideas?