That’s the menu you get by clicking the profile icon in the lower right. I’m talking about the one in the upper right:

You appear to be in the “Lemmy Web Preferences” section, not “Look and Feel.” Maybe we’re accessing settings from different places somehow: I go to my profile picture in the upper right corner, it pops open a half-menu, and I use the option at the bottom to access my settings.

I’m on Summit as well and have the option to block keywords.

Settings > Look and Feel > Post Feed > Filters > Keyword Filters

Then you can do the same thing under “Post and Comments” (instead of “Post Feed”) if you want even more blocking.