askubuntu.com/questions/1028633/host-name-reverts-to-old-name-after-reboot-in-18-04-lts
Norm (ノーム) 
@norm@shrimp.biribiri.dev
was wondering why the pi 4's hostname was being reset to the old one. turns out cloud-init by default resets the hostname to the one used for initial setup unless you tell it not to...
askubuntu.com/questions/1028633/host-name-reverts-to-old-name-after-reboot-in-18-04-lts
askubuntu.com/questions/1028633/host-name-reverts-to-old-name-after-reboot-in-18-04-lts