No we don't need / shouldn't use Docker. As jasomill guessed the disk size and memory usage that Docker needs is just unnecessary overhead. These devices have only 8 GiB disk space. systemd provides every single thing that we need; one can obtain equivalent isolation just with a systemd unit file.

If you don't need the layers of Docker and server pull-push, it is just overhead. We just fetch a single cryptographically signed squashfs file and execute the program in it with limited FS and separate namespaces.