I've been looking into the source code of many scripts here and on the web and found most of them have encrypted source code, connect to a central server and even some mine crypto.
I only need basic stuff (SSH, dropbear, squid)
Is there any clean, no backdoor, no mining script out there?
You don't need any "script" to install what you want. You can simply ssh into your VPS and install stuff there. Some scripts are only needed if you want them to get pre-configured for you.