Hi guys!

I am not so well educated with Linux systems... (just changed to mainly Linux a couple of months ago...) - so therefore please be patient with me and my questions...

I have really a special question for you guys... and I hope that somebody could help me solving this issue...

Ok, I explain first of all which situation I have:

I have a MacBook Air (2012) and partioned my SSD into 5 parts.
I made one partition with MacOS (Catalina) and APFS file system.
Another one partion for Windows 10 (in the moment still empty, need to install yet, but the partition is reserved for that manner) and NTFS file system.
2 partitions (a bigger and a smaller one) with KDE Neon and ext4 file system.
And last but not least, one big partition which should be used as "file storage" and this one has exFAT as file system.

I installed refind as bootmanager to be able to choose between all the different OS. So I can boot every system I want.

So far so good.

But now - here comes my big issue...

If I boot one of my KDE-Neon partitions (doesen't matter which one, because both are behaving in the same way!), and I open Dolphin to have a look on all partitions and data which will be shown to me, I recognized that I am able to see all 5 partitions.

I can not access only one partition - that is the MacOS one with the APFS file system, but all other partitions I am able to access!

That should not be the case, except for the exFAT partition - because this partition should be accessable for all OS versions on my computer.

The big problem I have now is, that if I boot KDE-Neon 1 then, I have root rights on the partition from KDE-Neon 1 and that's absolutely OK, because that is the active partition where I am active as root. BUT the problem is now that if I decide to access the KDE-Neon 2 partition with dolphin I can access it also as root and can therefore generate, delete, and copy files from that partition (KDE-Neon 2) - so I have full admin rights if I want to...

And that must not be the case!

So I generally would like to secure the partition form KDE-Neon 2 to restrict every access from outside in general. Nobody should be able to access this partition and should even be able to show which files and directorys are on it, except if I boot the KDE-Neon 2 partition.

So I myself should not be able to gain any kind of access to this KDE-Neon 2 partition as user when I booted MacOS, Windows 10 or KDE-Neon 1.

So therefore I should not be able to display the content of the KDE-Neon 2 partition in Dolphin file explorer when I booted KDE-Neon 1.

So my big question is now:

How can I restrict any kind of access from other users (regardless if they have root rights in their environment or not) to my KDE-Neon 2 partition when I am not active as root user from KDE-Neon 2?

Where can I set this up and protect my KDE-Neon 2 partition?

I would be very happy if somebody could help me, because I searched a lot of other linux (especially ubuntu) forums but I wasn't able to find the right answer!

Thank you very much and I am looking forward to your replies