Sorry for the late response, I was on vacation.
This to me is basic computer knowledge.
You should always browse the web via https. Right?
Okay, the next thing is more complicated. But I try to explain it.
The /owncloud makes sense if you think about it. You have a server, right?
On that server you can have multiple applications, right? How would you access them?
You know that your server is on 192.168.178.1, right?
But you installed ownCloud and nextcloud. How would you tell your browser - Go to ownCloud? Well, you need a name what you can call. This is specified in your apache configuration.
You specify that if you enter your server address and /owncloud you will access ownCloud and /nextcloud will take you to nextcloud.
Honestly? It’s the first time I am hearing this. I have installed ownCloud 100s of times for testing and never did I run in to the problem you are describing. If you could provide steps to reproduce, I will try to reproduce it and get to the source of this issue.
surely you can understand that security is a high priority issue for ownCloud.
There is a guide how to get good certificates in the installation section of the documentation:
But my top question right now is - what manual / doc were you using and where would you expect improvement: what page what place and how. all this you can formulate and post in an issue on github https://github.com/owncloud/docs/issues or write it here and I will do it.