I bricked my phone after update and then reinstalling lipstick (I readed late that it isn't needed now) and instructions from first post didn't work.

But I recovered it by Recovery mode ---> Shell ---> mkdir /mnt/rootfs && mount /dev/mmcblk0p28 /mnt/rootfs && chroot /mnt/rootfs ---> I mounted proc sysfs and /dev/pts but maybe not needed

Then, to get internet in the Jolla in Recovery mode in my Debian GNU/Linux I done:

sysctl net.ipv4.ip_forward=1
iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE

And in my Jollaadded some nameservers to /etc/resolv.conf because if not, it can't resolve repo names to IPs and:
route add default gw 10.42.66.67

Finally I installed normal lipstick-qt5 with: zypper in -f lipstick-qt5
Unmounted sys proc and /dev/pts from the chroot. Can't umount /mnt/rootfs because /sbin/busybox-static and other processes were using it (info got by "lsof /mnt/rootfs" command). I done "killall -15 busybox-static" and telnet recovery mode closed ( I made a stupid killall) and phone rebooted.

And now works!!! Without having to reset it

I could make a better understandable guide if somebody ask...