Is it possible to use the same slug structure for a taxonomy and for some pages?

Figured out a solution! This intercepts the query at parse_request, checks if a page with a matching slug exists, and if so, changes the request to a page request.

/**
 * Fix rewrite conflicts between "project_category" and "page"
 *
 * @param WP $query
 * @return WP
 */
function prefix_parse_request_fix_rewrite_conflicts_project_category(WP $query): WP {
    if (isset($query->query_vars["project_category"])) {
        $path = preg_replace("/\//", "", $_SERVER["REQUEST_URI"]);

        if (get_page_by_path($path, OBJECT, "page")) {
            unset($query->query_vars["project_category"]);
            $query->query_vars["pagename"] = $path;
        }
    }

    return $query;
}
add_action("parse_request", "prefix_parse_request_fix_rewrite_conflicts_project_category");