I ordered a new cannister seal on Nov. 25, 2020.  It didn't arrive, I called customer service, another one was ordered and shipped, which I received around Dec. 27.  A month later. 
The Kohler website theoretically offered a video on how to replace the seal.  But what I saw re the cannister did NOT match mine, in my 5 year old toilet.  According to the Kohler video, the cannister could be removed by unscrewing the cap on top of the guide.  That could not happen with mine.
After another hour searching for some help, I found a video on YouTube that showed the same kind of cannister I have, and how to remove it.  It took me 5 minutes to then replace the seal, but about 31 days, 2 hours to get the seal and figure out how to replace it. So why didn't I call a plumber to come and replace that seal?  I didn't want anyone to come into my house during this pandemic.