New Tab Override allows you to set the page that shows whenever you open a new tab. Features

Change your new tab page to whatever website you like
You can use the pipe character (“|”) to randomly select a page from several pages
Use your current home page as new tab page
Customize the background color for your new tab page
Store a local HTML file in the extension and use it for new tab content
Get the latest news about Mozilla as new tab page (German language only)
You can set the focus to the address bar or the website
Customize where new tabs are opened
Automatically adds “https://” if protocol is missing from a URL
Can be used in conjunction with Firefox’s container tabs feature
Dark mode support for options interface

Shortcuts The settings interface can be accessed via Shift + F12. It is also possible to open the settings interface by entering newtab settings in the address bar or from the menu entry in the tools menu. Languages New Tab Override is currently available in the following languages:

English
German
French (Thanks, SuperPat45 and Mozilla commmunity!)
Chinese, Simplified (Thanks, tiansh and Mozilla commmunity!)
Spanish (Thanks, MissingUser and Mozilla commmunity!)
Italian (Thanks, Mozilla commmunity!)
Russian (Thanks, vanja-san!)
Dutch (Thanks, Tonnes!)
Turkish (Thanks, boranroni!)
Ukrainian (Thanks, Bergil32!)
Brazilian Portuguese (Thanks, Mozilla commmunity!)
Swedish (Thanks, Sopor-!)
Indonesian (Thanks, rosatiara!)
Polish (Thanks, WaldiPL!)
Upper Sorbian (Thanks, milupo!)
Lower Sorbian (Thanks, milupo!)

Permissions New Tab Override needs several permissions to work properly. Some permissions are mandatory, some are optional. To offer full transparency, this overview also lists "silent" permissions. Mandatory permissions. New Tab Override will not work without the following permissions: access browser history The permission to access the browser history is needed to prevent spammy "moz-extension://" entries in your browsing history every time you open a new tab. There is no way to prevent this without this permission. access browser tabs The permission to access the browser tabs is needed so that New Tab Override can jump to the settings page if it’s already open in another tab when you click the button to open the extension’s settings. read and modify browser settings The permission to read and modify browser settings is needed to change the position of new tabs and for the option to automatically use your home page as new tab page. Optional permissions. These permissions are not needed to install and use New Tab Override: access data for www.soeren-hentzschel.at The permission to access data for www.soeren-hentzschel.at is only needed if you enable the option to see the latest news about Mozilla as new tab page. If enabled, New Tab Override reads the feed of www.soeren-hentzschel.at to show you the latest news. Silent permissions. New Tab Override requires additional permissions, but Firefox does not prompt requests for the following: cookies The cookies permission is needed to prevent the loss of container information if the container tabs feature of Firefox is used. menus The menus permission is needed for providing an entry in the tools menu for accessing New Tab Override's settings. storage The storage permission is needed so that New Tab Override can store settings such as your new tab page.