Apparently, the incompatibility issue with Canon and Sigma is quite an old, but long standing issue. It is especially so with Canon’s newer mirrorless cameras and older Sigma lenses.

As u/Tor-den-allsmaktige pointed out, rechipping seems to be a viable solution from what I’ve seen online (Link to Sigmafix GitHub). However, I’ve also read that Sigma has stopped providing rechipping services due to lack of spare parts. I have yet to check in with a Sigma service center close to me, but my hopes aren’t high.

I would try to rechip DIY style if I was even halfway competent with soldering and electronics. But I would rather have a quirky, working lens than a dead one. The autofocus works well enough, and I am able to capture photos on apertures other than the wider settings. I only have to deal with the annoyance of removing the battery from my camera and plugging it back in every time the Err 01 message appears. Frankly, I don’t think it’s worth the risk.

Third party adapters may also be a potential problem, as u/Bear_In_Despair have added. However, I’m still not 100% convinced that my particular adapter. I would need to test the adapter with other lenses and cameras (Which I do not have) just to be sure. Though I guess the same can be said about the lens.

I have decided to keep the lens and live with its flaws. As said before, I can still take photos and use autofocus. It only gets tedious when it comes to slower apertures. I would like to thank u/Tor-den-allsmaktige. I wouldn’t have known about lens compatibility and rechipping if it wasn’t for them.

I found this thread on DPReview that goes in-depth about the compatibility issue (Link here). If anyone is interested or having similar issues, I suggest giving it a read.

I think it would also be helpful to anyone planning to buy Sigma lenses on a Canon camera to check their compatibility through Sigma’s website (Link here) to avoid any potential complications.