Can the Sigma TC-1401 1.4x Teleconverter be used with Canon lenses?

The site that sima has in Canada states the lens that will work with the multiplier. It only works up to F8. Beyond that it gets ? I’m going to use it on a 150-600 f4-5.6. So at longer range at higher Fstops it may go into manual mode D5 mark 2. But there is no fear of it hitting the mirror as it shoots. Ef (S) it May.

WRT mounting, check the dots on the mounts. EF (full-frame) lenses have a red dot, EF-S (APS-C sensor) lenses have a white dot. The EF-S lenses extend further into the camera body so will NOT mount to an EF TC. I have no problems mounting the Sigma 1.4 and 2.0 TCs to my (EF mount) Sigma 70-200 2.8 for use on my 500D but the TCs are useless on my (EF-S) kit lenses and my 60mm macro.

I've now had a chance to rent both the Sigma TC-1401 and a Canon EF 70-200 f/4 L, and can confirm they do work together - at least using my 700D.

Your primary concern should rather be whether the teleconverter that you are considering is compatible with the camera body with which you intend to use it.

I've never used the Sigma TC you are considering, but I have used third party TCs with Canon cameras and lenses. Sometimes they work. Sometimes they don't. That's the risk one takes with third party lenses, E-TTL flashes, TCs, batteries, etc. Since third party manufacturers reverse-engineer their products to work with other makers' cameras sometimes it happens that a newer model from Canon (or Nikon, Pentax, Sigma, etc.) will cause problems with older third party products. In the case of lenses sometimes the third party maker will update the firmware to make the lens compatible with the newer models.

I have a third party TC I bought back around 2011 or so that works with all of my Canon lenses on any Canon body that was released around 2011 or earlier. All of the lenses I own were designed and released before 2011, even if my particular copy in a case or two was made more recently. If the TC and any of my Canon EF mount lenses are mounted on my 5D Mark III (2012) or 7D Mark II (2014) it locks the camera completely up and the TC must be removed, the camera powered down, and the camera battery removed before the camera will respond to any of the controls. The same TC works fine with a Canon 7D and 5D Mark II.

Update: If Autofocus Microadjustment (AFMA) is disabled via menu on the newer cameras, the older Kenko TC will work with them. Unfortunately, AFMA is more critical with longer focal length lenses and lens/TC or lens/extender combinations than with wider angle lenses.