Another config example without HTTPS, but with Apache Basic Auth HTTP login.
The user will connect to Apache on port 3333 and will be asked to log in. If authentification is successful, Apache will redirect the user to Invidious' page.
To make the VirtualHost config below actually work, you should as well:
Open port 3333 (or any other free port) adding Listen 3333 to Apache ports.conf (Debian /etc/apache2/ports.conf)
If you run Invidious with default parameters, you may need to replace default host binding (0.0.0.0) with localhost (127.0.0.1) instead. That way, Invidious won't be publicly available on port 3000 anymore, but only accessible via the reverse proxy on port 3333. So if you run Invidious via a systemd service, you would edit the service file (e.g. /etc/systemd/system/invidious.service) and modify the ExecStart line to include the -b switch as follows ExecStart=/home/invidious/invidious/invidious -b 127.0.0.1 -o invidious.log and then reload the daemon with systemctl daemon-reload so that changes are taken into account.
A convenient way to open such protected Invidious page without having to log in manually everytime is to access use a URL with the following format: http://username:password@domain:3333
ServerName invidious.domain.tld #add your own domain name (or localhost if you have none)
Deny from all # Forbid access to all by default...
#Allow from 127.0.0.1 #...Except from specific IPs (which will not need to authenticate)...
AuthUserFile /etc/apache2/.htpasswd #path to .htpasswd file
AuthName "Restricted Area" # name displayed in the promptbox
AuthType Basic # http://httpd.apache.org/docs/current/howto/auth.html
Require valid-user # ...and except from authenticated users included in the .htpasswd file
ProxyPass / http://127.0.0.1:3000/ nocanon
ProxyPassReverse / http://127.0.0.1:3000/
CustomLog /dev/null combined