2 urls are created for each page (with and without .html) and that hurts SEO about monadical.com HOT 2 OPEN

this site is using GH pages, and it looks like GH doesn't provide a way to redirect pages.
improvements that can be done:

• remove .html pages from all internal links
• remove .html from canonical tag URL
  

https://stackoverflow.com/questions/21244910/remove-html-extension-from-github-pages

from monadical.com.

tried 2 ways I could think of:

1. remove .html from content.json, which is responsible for mapping URL to html pages:

--- a/content.json
+++ b/content.json
@@ -9,7 +9,7 @@
     },
     "about": {
       "title": "About",
-      "url": "/about.html",
+      "url": "/about",
       "template": "about.html"
     },
     "blog": {

issue: works in dev server but doesn't work in local prod server after building output. about page is getting generated without the .html extension. it most likely won't work after deploying to github server as pages extensions are removed.

2. replace .html from links using jinja2 replace filter

--- a/templates/base.html
+++ b/templates/base.html
@@ -157,7 +157,7 @@
                         <li>
                             <b>Monadical</b>
                         </li>
-                        <a href="{{PAGES.blog.url}}">Blog</a>
+                        <a href="{{PAGES.blog.url|replace('.html','')}}">Blog</a>
                         <li><a href="{{PAGES.services.url}}">Services</a></li>

issues: links won't work in dev server and local prod server after building output, but it'll work after deployment as github server maps links w/o .html at end to .html files with same name.

from monadical.com.