Posts work, Categories work, Pages don’t

On my working site, i cant seem to view any capital-P Page, though i can view posts, custom posts types, archive pages, category pages, anything else, so it seems.
When i click the link to visit either of the two pages i’ve published, (example: https://kutd.jasandbox.ca/update-fsi-quantity/) I am brought back to the home.php template
I’ve done these things and the problem still exists:
I’ve changed the theme, I’ve reset my permalinks, I’ve updated WordPress, I’ve turned off all plugins.

I know that the page template works, because if i set my theme to use a static front page instead of posts,

The only thing that appears to make a difference is if i reset permalinks to Plain (ugly). With permalinks set to plain i can view Pages again, but then I can’t view any custom post type archive pages. (And of course, ugly permalinks is not ideal for the final product)

If it’s not the theme, and appears to not be the plugins, I presume it must be in the permalinks? But what in the permalinks can be messed up so it doesn’t show Pages but still works for other post types? And how to fix?

The page I need help with: [log in to see the link]