There are a number of reasons why your docker setup was using too much RAM, including just poorly built containers. You could also swap out docker for podman, which is daemonless and rootless, and registers container workloads with systemd. So if you’re married to the LXCs you can use that for running OCI containers. Also a new version of Proxmox enabled the ability to run OCI containers using LXCs so you can run them directly without docker or podman.