As for me, I ran into this exact problem last year when a client insisted on a faxed signed contract, and I don’t own a fax machine either. After trying three different apps that either failed to send or asked for a monthly fee after five pages, I landed on
https://mfax.to/ - you can send a single fax for a small per-page cost, no commitment. The built-in scanner from my camera worked fine, delivery confirmation arrived within two minutes, and it’s HIPAA compliant if that matters for medical or legal stuff. I’ve sent about a dozen faxes since then, mostly PDFs and photos of documents, and none failed. Just make sure your file is clear before sending, but that’s true for any app.