Burn-n-boot pihole

This post https://www.raspberrypi.org/forums/viewtopic.php?f=63&t=231762 has made me thinking if I could burn-n-boot pihole onto a spare SD card and swap it in my RPI without the family noticing it. Since the lockdown the entire family is constantly hooked on the net so pihole has become a critical component of the peace at home.

The process was successful but not flawless. Here is my workflow with findings:
First I booted Debian with Raspberry Pi Desktop on my ThinkPad from persistent live USB.
Then started the workflow with writing newest Raspbian on an SD card with Imager.
sudo fdisk -l
gave me that the SD card is disk /dev/sda
sudo mkdir /mnt/raspbian
sudo mount /dev/sda2 /mnt/raspbian
sudo mount /dev/sda1 /mnt/raspbian/boot
sudo systemd-nspawn -D /mnt/raspbian
and here I arrived at the first hiccup:

ERROR: ld.so: object '/usr/lib/arm-linux-gnueabihf/libarmmem-${PLATFORM}.so' from /etc/ld.so.preload cannot be preloaded (cannot open shared object file): ignored.

I could get rid of this ERROR by commenting the only line in /etc/ld.so.preload that contained the shared object file that cannot open.
apt update
apt -y upgrade
there was some hiccup:
System has not been booted with systemd as init system (PID 1). Can't operate
invoke-rc.d: could not determine current runlevel
Warning: using insecure memory!
but the upgrade eventually finished.
curl -sSL https://install.pi-hole.net | bash
Here I arrived some more hiccups

[✗] Checking apt-get for upgraded packages
Kernel update detected. If the install fails, please reboot and try again
SELinux not detected
Unsupported setsockopt level=270 optname=11
Unknown host QEMU_IFLA type: 50
Unknown host QEMU_IFLA type: 51
Unknown host RTA type: 25

when I tried to set-up static IP I got kicked out with:

RTNETLINK answers: Operation not permitted

but I could see the changed static IP in /etc/dhcpcd.conf

interface eth0
        static ip_address=192.168.1.3/24
        static routers=192.168.1.1
        static domain_name_servers=8.8.8.8 8.8.4.4

so when run pihole install script again it did accept the static IP settings because:

Static IP already configured

then some more checks failed:

[✗] Check for existing repository in /etc/.pihole
[✗] Check for existing repository in /var/www/html/admin

but ultimately the install finished.
Removed webserver password and copied over dhcp config from running server:
pihole -a -p
scp jordana@192.168.1.3:/etc/dnsmasq.d/02-pihole-dhcp.conf /etc/dnsmasq.d 
scp jordana@192.168.1.3:/etc/dnsmasq.d/04-pihole-static-dhcp.conf /etc/dnsmasq.d
then finished with some user management and enabled ssh:
groups pi
useradd -m -G <all-pi-groups-comma-separated> jordana
passwd pi
passwd jordana
touch /boot/ssh
exit
finally umount and ejected the SD card
sudo umount /mnt/raspbian/boot
sudo umount /mnt/raspbian
Popping the SD card into my RPI booted nicely and I could ssh with configured user but pihole was not running.
Not sure what is wrong but only repair seemed to fix it.
pihole -r
While the repair process was reasonably fast so I only got angry looks for a minute or two I am wondering how could this workflow be improved so that pihole would just start after burn-n-boot without repair?