And there’s not really any mental gymnastics involved in “racists exist.”

That is not what the question is, nor the conclusion.

The question is, "Who put this flyer up?"

And of the answers:

Option 1: Genuine Racist

• They possessed the capacity to produce this fairly well made flyer, despite the fact the venn diagram of "person who can make a flyer of this quality" and "person who is openly racist" is a very thin sliver (unlikely occurrence #1)
• They did not have any existing members of an "in group", and made the telegram "pre-emptively" (extremely uncommon, typically people of the group precede the creation of a chat room to chat in, unlikely occurrence #2)
• They setup a proton email, an extremely uncommon tool typically only used by extremely tech savvy individuals, but didnt put in the extra work to make it have a real account name which is extremely uncommon (unlikely occurrence #3)
• They telegram group has a photo of the exact same paper that was "discovered" shortly after, but on a table, and the photo was set only a short period of time before it was "discovered" and posted to social media. Which means the individual took the photo, set the picture of the telegram group, went outside to put the flyer up, and in under 1-2 hours it was already posted up to social media and shared with the news. (unlikely occurrence #4)
• The group who discovered and shared this picture happened to be discovered by the owner of a social media group "BlackVancouver" who happens to also be a group specifically focused on spreading awareness about racist acts in the area. They were exactly in the right place at the right time to find this picture literally moments after it was put up? (extremely unlikely occurrence #5)
• Despite this, no other pictures at all of these flyers have surfaced anywhere else, which seems to mean that one single flyer was posted and was taken down as soon as it was found. No one else has any info on this flyer except the couple pictures shared by BlackVancouver. It's very unlikely that a person who made flyers for their group would put all that effort into making the flyer and proceed to post up literally just one of them. (unlikely occurrence #6)
• The telegram group has had no members added, and no posts made after the sharing of the flyer with the news outlet (unlikely occurrence #7)

Option 2: Someone fostering fake outrage to boost their social media

• A person who manages a social media account is not that unlikely to possess the skills to make a fairly decent looking flyer
• If they were making a fake telegram to add "face value" authenticity to their flyer, the lack of any members of the telegram group is not unexpected
• A proton email would be not unheard of to be utilized by someone looking to setup a quick and dirty fake email to add further authenticity to their flyer
• Wanting to quickly slap together the telegram group in as low effort as possible while still trying to create the appearance of being real at face value, using the flyer itself as the picture of their fake telegram group is a quick and dirty solution, and it would make sense that they would have taken the picture for it shortly before going outside to put the flyer up
• The group discovering the flyer being the one who made it is self explanatory at this point, as that is the goal, no longer a coincidence but by design
• The individual would not want to get in trouble, so they would have only made a single fake flyer, tacked it up, snapped a picture, then took it down asap, explaining why there aren't any other photos that have surfaced of the flyer and why it seems like only a single flyer ever got posted up.
• The individual, once satisfied that everything looks legit and enough outrage has generated, locked the telegram group and abandoned it, as it has now served its purpose.

Note how the first option requires enormous mental gymnastics to make sense, whereas the latter largely fits within its own context and doesnt require any stretching to conclude. All the "unlikely coincidences" in scenario 1 become expected results in scenario 2.

Thus... Occam's Razor concludes that situation 2 is way way more likely, and is the one to default to.

If you can come up with an even more likely scenario than situation 2 though, by all means, lets hear it. But I don't see anyway this narrative fits some random racist mom and tot group founder without having to make numerous extremely unlikely assumptions.