Welcome to the community!
According to the Canadian website, these are the specifications for that phone:
MIMO: 5GNR: n2/66/25; LTE: B2/4/25/66/41
Judging by those specifications, that phone should have all of the compatible bands/frequencies. You can verify the compatible bands/frequencies here. You are correct in that Fido does not currently offer 5G service. While the phone should work on the networks, you should note that since Fido does not offer OnePlus devices, it's unlikely certain features (ie voLTE and/or Wifi-calling) will work with that device. You should also note that other versions of that device may not have the same band/frequency specifications.
Hope this helps 😀