Is it possible/fine to run Prometheus, Loki, Grafana outside of Kubernetes?
Yes--absolutely you can skip Kubernetes. Suggest that you still use Docker, but you could even just install the components separately.
I think it's easiest using Docker Compose (need to have package docker-compose installed on your host) to manage the containers.
Here is a docker-compose.yml that might be helpful:
version: '3'

services:
    prometheus:
        image: prom/prometheus:latest
        restart: unless-stopped
        ports:
            - &quot;9090:9090&quot;
        volumes:
            - /home/${USER}/opt/prometheus/data:/opt/prometheus/data:rw
            - /home/${USER}/opt/prometheus/config:/opt/prometheus/config:rw
        environment:
            SERVER_KEY: ${SERVER_KEY}
            SERVER_CERT: ${SERVER_CERT}

    grafana:
        image: grafana/grafana:latest
        restart: unless-stopped
        ports:
            - &quot;3000:3000&quot;
        volumes:
            - /home/${USER}/var/lib/grafana:/var/lib/grafana:rw
            - /home/${USER}/var/log/grafana:/var/log/grafana:rw
            - /home/${USER}/etc/grafana/grafana.ini:/etc/grafana/grafana.ini:rw
            - /home/${USER}/etc/grafana/ldap.toml:/etc/grafana/ldap.toml:rw
        environment:
            SERVER_KEY: ${SERVER_KEY}
            SERVER_CERT: ${SERVER_CERT}
            GF_SECURITY_ADMIN_USER: ${GF_SECURITY_ADMIN_USER}
            GF_SECURITY_ADMIN_PASSWORD: ${GF_SECURITY_ADMIN_PASSWORD}
        depends_on:
            - &quot;prometheus&quot;

Can also use Docker Compose for Loki and Promtail.
Docker Compose reference: https://docs.docker.com/compose/compose-file