Turris 1.x has a processor - Freescale P2020. It isn’t arm7l, but power architecture.
If you’d like to create LXC container of Turris OS, that’s possible through lxc-create. However, there is no Debian Stretch, but a port of Debian for PowerPCSPE, which is highly experimental. For it, you’d need to follow this documentation.
Many people including me have it running. You can take a look here: LXC kontejnery na Turris verze 1.x