It seems like NextcloudPi (or at least this specific install script) requires Debian 11 “Bullseye” in order to work…
https://github.com/nextcloud/nextcloudpi/blob/master/etc/library.sh
function check_distro()
{
local cfg="${1:-$NCPCFG}"
local supported=$(jq -r .release "$cfg")
grep -q "$supported" <(lsb_release -sc) && return 0
return 1
}
https://github.com/nextcloud/nextcloudpi/blob/master/install.sh
# check distro
check_distro etc/ncp.cfg || {
echo "ERROR: distro not supported:";
cat /etc/issue
exit 1;
}
Probably not… I mean, you could of course just remove the check from the script, but I assume there is a good reason why this check was added, which means that if you run this on Ubuntu, it would most likely cause issues further down the road, or maybe it won’t even install properly. So I would recommend you to install Debian 11 on your device.
Or you could try another appliance / installation method like Nextcloud-AIO or the Snap package. Unfortunately I don’t know if these are arm64 compatible.
If none of this works, there’s of course always the possibility of a manual installation.
Good luck.