Prevent encrypted APFS volume on partition to automount / ask for password on login - Catalina I know similar questions have been asked before but I just can't believe this can't be solved, so I am going to ask again with specific details.
I have two partitions that are bootable on the internal drive of my Mac running macOS Catalina 10.15.7. Both are encrypted APFS volumes.
Whenever I log in to one of them, I am getting a promt, asking me for the password of the other. I do not want to store the password in the keychain to work around the prompt (for security reasons), in fact I do not want the other volume to be automatically mounted at all.
All I want is to be able to choose the boot volume on startup (via the [Opt] key).

I tried

adding this line to my /etc/fstab using vifs:

UUID=&lt;UUID of the volume&gt; none apfs rw,noauto

but this does not prevent the prompt from appearing.

changing the volume role via

diskutil ap changeVolumeRole &lt;diskId&gt; D

but this returns the error: Error setting APFS Volume role: Unable to set the APFS Volume Role (-69599)

Is there seriously no way of preventing disks from being automounted?
Can the Finder be at leat taught to not ask for the password?
Starting with MacOS BigSur 11.1. the /etc/fstab/ solution works (again):

find the volume label from the volume name:
diskutil list | grep &lt;volume name&gt;
the last entry (e.g. disk2s2) is the volume label.
find out the volume UUID from the volume label
diskutil info &lt;volume label&gt; | grep &quot;Volume UUID&quot;
open /etc/fstab for editing:
sudo vifs
add a line preventing the auto-mount of the volume:
UUID=&lt;volume uuid&gt; none auto noauto

Here's a complete example:
&gt; diskutil list | grep &quot;Macintosh HD2 - Data&quot;
2:                APFS Volume Macintosh HD2 - Data⁩       341.8 GB   disk2s2

&gt; diskutil info disk2s2 | grep &quot;Volume UUID&quot;
Volume UUID:               C58A1BDC-593C-4854-B954-702A73ABD67C

&gt; sudo vifs
# add the following line:
UUID=C58A1BDC-593C-4854-B954-702A73ABD67C none auto noauto

On the next reboot the popup asking for the password will no longer appear.