For full-frame Canon, the short answer is: not really, at least not with standard front-mounted filters.

At around 12mm on full frame, rectilinear lenses are so wide that they typically need a large protruding front element. That prevents normal front filter mounting and makes vignetting a problem. Community answers note that Sigma’s 12-24mm is the main rectilinear option in this range, but these lenses generally do not support front filters with systems like Lee.

If you’re open to fisheye lenses, options like the Canon EF 8-15mm f/4L Fisheye and Sigma fisheyes can use rear gelatin filters instead of front filters. The original Sigma 12-24mm was also noted as accepting rear gel filters, but not the newer II version.

So if your requirement is a true 12mm full-frame zoom plus front-mounted ND filters, there effectively isn’t a suitable option in the lenses discussed. Rear gel filters may be the only workaround, but they’re less convenient and won’t replace all front-filter uses. Also, for ultra-wide landscapes, a CPL is often not ideal anyway because polarization can look uneven across a wide sky.