You can still get the Google Coral (both the USB dongle and M.2/PCIe versions), but Google has effectively abandoned the official drivers. You'll need to use community-maintained DKMS drivers if you go with the PCIe version on newer Linux kernels.

If you want a modern alternative, look into the Hailo-8 or Hailo-8L M.2 AI accelerators. They plug right into an open M.2 slot and natively integrate into recent versions of Frigate. Keep in mind that these accelerators ONLY process object detection inference - they do not handle video decoding.

For video decoding, your OptiPlex 7070's Intel CPU has Quick Sync Video (QSV). You can pass /dev/dri through to your container, and Intel iGPU hardware acceleration will handle decoding the RTSP streams with minimal CPU overhead.

If you prefer an all-in-one approach, an Intel or Nvidia GPU can handle both video decoding and object detection (via OpenVINO or TensorRT), but a Micro PC limits your physical expansion options.

Storing recordings on a TrueNAS share over NFS or SMB works just fine. Mount the NFS share directly in Proxmox or the VM host, then pass the directory through to your Docker container.