How to save an HTML page from a web site using Chrome
The simplest thing I can think of is to open the file you want to save as source code, which you can do from Chrome Android by prepending view-source to the URL, like so.
view-source:https://my-site.tld/xxx/my_page.html

You can then either copy and paste this code into a local file, or use the share button to open it with a compatible app of your choosing.
If this seems like too much of a pain, you might consider doing something like using PHP to determine whether the file should be viewed or downloaded. For example if the IP address of the request matches your phone, download instead of displaying the file.
&lt;?php
/**
 * File url: https://my-site.tld/xxx/my_page.php
 *
 */

$remote_address = filter_input(INPUT_SERVER, 'REMOTE_ADDR', FILTER_SANITIZE_STRING);

if ($remote_address === '56.57.58.59') {
    header(&quot;Content-Disposition: attachment; filename=\&quot;filename.html\&quot;\n&quot;);
    header(&quot;Content-Type: text/html\n&quot;);
}

?&gt;
&lt;!-- Begin actual page content --&gt;
&lt;!DOCTYPE html&gt;
&lt;html lang=&quot;en-US&quot;&gt;
    &lt;meta charset=&quot;UTF-8&quot;&gt;
    ....

Conversely, you could also simply create a separate page to allow a download regardless of the requesting IP address.
&lt;?php
/**
 * File url: https://my-site.tld/xxx/my_page-download.php
 *
 */

header(&quot;Content-Disposition: attachment; filename=\&quot;filename.html\&quot;\n&quot;);
header(&quot;Content-Type: text/html\n&quot;);
readfile('path/to/file');

Additional information about the Content-Disposition header may be found in the Mozilla Developer Docs. It's not the only resource, of course, it's just my personal favorite.