Best way to fax from M1 MacBook Pro

Without a landline, you would have to look for a special fax service. I have not tried a service like that (can still use a fax machine, if absolutely necessary), but this would be just one example: https://www.hpsmart.com/us/en/mobile-fax/faq .

Most users are perfectly happy to receive a fax-format file or a pdf as an email attachment instead of actually forcing you transmit a traditional fax.