I'm using Firefox and Chrome browsers on an old Windows XP laptop for testing because it has a small screen size... I'm also using the Firefox browser on an Android 10 phone. From the Windows Firefox browser, I ran http://jerrypeek.com/gallery/piwigo-netinstall.php yesterday. After logging on as admin, I found that I couldn't access the bottom entries in the left-hand menu: Tools and Configuration. If I tried to click near the bottom, I'd get the Piwigo website from the link "floating" over the menu. See the first screenshot below.

I can work around the problem by using the browser's "Zoom Out" command, Ctrl-minus (Ctrl-dash), to shrink the contents until the bottom of the menu is visible. See the second screen shot; I circled the zoom percentage in red.

My browser window is 1005x546 pixels. Could Piwigo automatically add a scroll bar or something if the left-side menu doesn't fit?

(BTW, I know that the window title is <img src="..." etc. I temporarily put HTML code in the Gallery Title until I can find out how to put an image there.) I'm running Piwigo on a 1&1 IONOS shared hosting package; they use Apache, MySQL 5.7 and PHP 7.3. (They'll downgrade me to PHP 7.1 if I pay an extra $10/month, which I'd rather not do if I don't have to.) If you want more info, go to http://jerrypeek.com/phpinfo.php .

Piwigo version: 2.10.1
PHP version: 7.3
MySQL version: 5.7
Piwigo URL: http://jerrypeek.com/gallery/