"Your data directory is not writable" after Ubuntu upgrade

[scubamuc]

alternatively you could connect local directories as described here:

How to add samba shares and local shares to Nextcloud snap

How to add samba shares and local shares to Nextcloud snap as external-storage Snap confinement is a security feature and determines the amount of access an application has to system resources, such as files, the network, peripherals and services. Thus your Nextcloud snap is securely confined from the host system. Unless you specifically allow the Nextcloud snap to access the /media or /mnt directories on the host system, you will not be able to access any other directory outside of the confine…

now its clear you’re not using the snap, but the method is similar regardless of the installation method.