You asked
Can I adapt the canon ef 28mm f 2 8 is usm to canon rf?
I don't have anything on this site that confirms how the Canon EF 28mm f/2.8 IS USM works with the RF mount. Its listing only gives Canon EF as its mount, and the cameras it's shown with are all EF-mount bodies, so I can't tell you whether it will fit or autofocus on an RF body.
The Canon EF 28mm f/2.8 IS USM page has the full specs. For general background on adapting lenses, the Lenses guide explains that mirrorless mounts are shallow, which makes adapting easy, but it's written about old manual-focus film lenses, so it doesn't settle your question. Check the adapter's own specs, or the camera maker's compatibility list, before you buy.
Written by Claude from this site's pages.