For a Grandstream ATA/router (HT8xx or similar), the cheapest and least-effort path is a pay-as-you-go SIP trunk provider — no PBX needed, just point the device at the provider's SIP registrar.

VoIP.ms is the standard answer for this. Canadian DIDs start at $0.85/month with no-contract, metered pricing, and outbound Canada/US calls from $0.005/minute. Grandstream devices are natively supported — VoIP.ms even publishes provisioning templates for most Grandstream models, so setup is essentially: create account, buy a DID, plug in the server/username/password on the ATA, done. This is what most homelab/self-host people use.

Callcentric (US-based) is the other common "cheap effort" pick — free incoming DID if you make one outbound call every 90 days, no monthly minimum, works fine with any standard SIP ATA. Slightly less Canada-friendly than VoIP.ms but dead simple to configure.

DIDLogic is worth a mention if you want wholesale-tier per-minute rates around $0.002–$0.003/minute to Canadian destinations, though it's a bit more oriented toward businesses than plug-and-play home use.If you want the absolute minimum-effort path: VoIP.ms + a Grandstream ATA is basically the canonical setup for this — buy a DID, plug in the SIP creds using their Grandstream template, done in under 15 minutes.