Lemmy.ca's Main Community

Hello. I recently joined Lemmy, and quite like it. I have been on Mastodon for a while. So, I was interested in following some of the communities and posts here on Lemmy within my Mastodon account. I did manage to successfully follow two communities from this instance, those being NDP and Ontario. However, other communities, such as Toronto, Biking, Canada, and some others, the search turned up empty (I had a screenshot to better illustrate this, but I was given a syntax error when I tried to upload it). So, I was unable to follow them on Mastodon.

Of the communities that I did manage to follow, I have been able to interact with them using my Mastodon account. However, some actions have not been as I expected them to be. I would put a hashtag in the title of a post here on Lemmy, expecting this to show up in a hashtag search on Mastodon (since, you know, we're all federated), but this didn't work. The post, when I search for it, appears on Mastodon, but it does not appear in a search of the included hashtag (which I find odd). But I digress.

My main question is why can I find and follow some Lemmy communities on Mastodon but some I simply cannot?