VWRA (all world UCITS) probably the more famous one charging 0.22%, while the closest corresponding US ETF VT (total world) is just 0.06% (dropped from 0.07%)
Basically, they have different use cases. Docker is designed to run a single application with immutable volume, while LXD is designed to run a (mutable) OS, like a VM. Sure, you can use Docker run an OS, but it is not designed for that.
Imagine you need to install an application that will install/persist some files to /etc, some files to /var, some files to /bin... etc. In Docker, you will need to install that application during build time, specify volume path, specify the ENTRYPOINT to the application and use the resulting image to run it. In LXD, you can exec into the container and install it, setup systemd service to run it on startup - exactly like what you would do in a VM.
What about Docker's design is incompatible with running systemd? Because that seems to be mainly what LXD containers offer over typical docker containers.
Even non-free tier burstable VM is super cheap. For example, a VM.Standard.E4.Flex (AMD x86) with 1 OCPU (2 vCPU) and 4GB RAM with burstable baseline 50% is just ~$13.05/month (($0.025*50% + 4*$0.0015)*730hr). With baseline 12.5% it is just ~$6.66/month.
In comparison, AWS t3a.medium (2vCPU, 4GB RAM, burstable baseline 20%) will cost ~$27.45/month ($0.0376*730hr). DigitalOcean's 2vCPU 4GB Droplet will cost $24/month.
Hetzner deserves way more attention in the VPS space. They offer an equivalent configuration for just €5.32/month, and I'm not even rounding anything down.
And for about the same price that AWS offers for their weak boxes ("~$27.45/mo"), Hetzner will give you 8 vCPUs and 16 GB of RAM... Yes, the IPv4 cost is excluded, but it's only €0.61/month if you even want to have it.