"DMARC does not stop them" should be printed on every email admin's monitor.

On actually doing the lookalike monitoring, since that's where teams tend to stall: dnstwist on a schedule against your own domain is a fine free start. Where it gets thin is homoglyph variants and brand-plus-keyword names like yourbrand-support, which are exactly what BEC crews use for executive impersonation.

If you'd rather not run that yourself, WhoisFreaks Brand Monitoring scans new registrations twice a day for typos, homoglyphs, keyword combos and TLD swaps, and alerts by email or webhook. Disclosure: I work there. There's a one-brand trial on request.

Either way, the output slots nicely into your week-two gateway review as the list behind "domains that look like your own."