That’s already a thing.
There is plenty of self-hosted documentation provided to you free of charge here.
You can use the hosted version of Invoice Ninja at https://invoiceninja.com, the plans start from just $0 a month.
You shouldn’t be using server.php. This was stated in a reply to your post three years ago: https://forum2.invoiceninja.com/t/cannot-get-signature-on-pro-version-of-invoice-ninja/3008/8
I recommend using Softaculous to install Invoice Ninja as it sounds like you are having trouble installing it manually (I can’t really see any benefit to installing it manually anyways). It still has a v4 release available that you can install too!
But if you are really wanting to install it manually then drag the uncompressed files from Release Minor fixes · invoiceninja/invoiceninja · GitHub into your public_html directory and configure your .env file accordingly with your domain. Then navigate to your domain via your web browser and you should be greeted with a setup page.
What is in your storage/logs/laravel-error.log file?
I recommend finding another hosting provider if uploading a file via FTP took hours. It sounds like you are also using cPanel which already has a built-in file uploader implemented in the file manager.