I know I’ve personally ran into some issues when I attempted to install docker in an LXC container on my home server.
While I didn’t end up attempting to install Bitwarden in the LXC it could very well be a similar issue. I found this guide below on how to install portainer in a Proxmox LXC, which may help to assist you. https://apacheiot.org/docker/how-to-install-docker-portainer-lxc-container-proxmox/
Presumably much of the steps will be the same to first install the docker engine and then enable docker in the LXC.
I would try these first and see if you can get docker to run inside of the LXC first before attempting to run the install script. Then let us know how that goes
I also note that your config is set to the minimum requirements, you may also wish to up this to the recommend 4GB for self-hosting on the standard install.
I have installed LXC Debian 11 with LAMP for a long time.
LXC configuration (see first post).
Now I want to add Bitwarden. My procedure is the same as on this website.