Fulltext installation error on ubuntu 20.04 in LXC

Steps to reproduce

1. Install ubuntu 20.04 on an LXC
2. Run the script

Expected behaviour

Installation ok.

Server configuration

Nextcloud server version:
Nextcloud 19.0.3

Server OS (Ubuntu server is default)
Ubuntu 20.04
LXC Config:
root@ns508187:/etc/pve/lxc# cat 109.conf
arch: amd64
cmode: shell
cores: 8
features: fuse=1,nesting=1
hostname: cloudct
memory: 8500
nameserver: 1.1.1.1
net0: name=eth0,bridge=vmbr0,firewall=1,gw=167.114.64.254,hwaddr=02:00:00:6c:ec:09,ip=198.27.104.122/32,type=veth
onboot: 1
ostype: ubuntu
rootfs: local:109/vm-109-disk-12.raw,size=100G
swap: 512
unprivileged: 1
lxc.apparmor.raw: mount,

How did you install the VM? (Scripted install from master OR Released version)
master

Network

Do you use DHCP?
no

Is port 80 and/or 443 open?
yes

Logs / Screenshots

167399fc39c8: Pull complete
Digest: sha256:acdae9839d02d50688a603566b1bb075ba81755c9db2f4c93c05482513940481
Status: Downloaded newer image for ark74/nc_fts:latest
docker.io/ark74/nc_fts:latest
a1f0dbfc02578f40b6460d60191c420a3499951c590f0acd84f2e9612d9d77c6
docker: Error response from daemon: OCI runtime create failed: container_linux.go:349: starting container process caused "process_linux.go:449: container init caused "process_linux.go:378: setting rlimits for ready process caused \"error setting rlimit type 8: operation not permitted\""": unknown.
Error response from daemon: Cannot restart container fts_esror: OCI runtime create failed: container_linux.go:349: starting container process caused "process_linux.go:449: container init caused "process_linux.go:378: setting rlimits for ready process caused \"error setting rlimit type 8: operation not permitted\""": unknown
Waiting for docker bootstraping...
Installing fulltextsearch...
fulltextsearch already enabled
Installing fulltextsearch_elasticsearch...
fulltextsearch_elasticsearch already enabled
Installing files_fulltextsearch...
files_fulltextsearch already enabled
{
"search_platform": "OCA\FullTextSearch_ElasticSearch\Platform\ElasticSearchPlatform",
"app_navigation": "0",
"provider_indexed": "",
"cron_err_reset": "1600724101",
"tick_ttl": "1800"
}
{
"elastic_host": "http://jficbledpbapojuwozihksyaqggi:qymwMF4BzwOOfqNiXG3lpp3Pn8Nu@localhost:9200",
"elastic_index": "jficbledpbapojuwozihksyaqggi-index",
"fields_limit": "10000",
"es_ver_below66": "0",
"analyzer_tokenizer": "standard"
}
{
"files_local": "1",
"files_external": "0",
"files_group_folders": "0",
"files_encrypted": "0",
"files_federated": "0",
"files_size": "20",
"files_pdf": "1",
"files_office": "1",
"files_image": "0",
"files_audio": "0"
}

In StaticNoPingConnectionPool.php line 50:

No alive nodes found in your cluster

fulltextsearch:index [--output [OUTPUT]] [-r|--no-readline] [--] []

Sorry but something went wrong. Please report this issue to https://github.com/nextcloud/vm/issues and include the output of the error message. Thank you!
sudo -u www-data php /var/www/nextcloud/occ fulltextsearch:index failed
Posting notification to users that are admins, this might take a while...
Posting 'Sorry but something went wrong. Please report this issue to https://github.com/nextcloud/vm/issues and include the output of the error message. Thank you!' to: admin

Screenshoots

https://imgur.com/a/4iVZVS5

Start by reproducing the reported script failure on Ubuntu 20.04 in the described LXC configuration, then inspect the Docker container fts_esror and the error at StaticNoPingConnectionPool.php line 50. The issue is resolved when the Elasticsearch container starts successfully and sudo -u www-data php /var/www/nextcloud/occ fulltextsearch:index completes.