Installation was like:

# ./veracrypt-1.19-setup-gui-x64

From 1.24 onward use

# dpkg -i *.deb

Missing dependencies were easily fixe with

# apt --fix-broken install

Using TC/VC as user requires sudo and an entry in the sudoers:

user  ALL=(root) NOPASSWD: /usr/bin/veracrypt

Add the correct username for "user".

Hm, I got something wrong, I guess.
Tried the ..-gtk3-gui and was asked for admin rights. Does this work only with sudo rights? So do I need to have the user in sudoers?

Yes, it will do a system-wide installation so it definitely needs the admin password.

Have you tried zulucrypt-gui? It's only an apt-get away.

It may also be worth learning how to do this manually with LUKS+LVM. This can come in quite handy if you don't have a GUI available and applies to encrypted volumes on regular hard drives as well.

Here's an example for a USB stick, assuming the drive is on /dev/sdb:

# set up encryption
sudo cryptsetup -s 512 -y luksFormat /dev/sdb1

# open encrypted volume
sudo cryptsetup luksOpen /dev/sdb1 data

# create physical volume
pvcreate /dev/mapper/data

# create volume group
vgcreate usb-vg /dev/mapper/data 

# create logical volume
lvcreate -l 100%FREE -n mydata usb-vg

# make nodes
sudo vgscan --mknodes

# activate logical volume
sudo vgchange -ay

# create FS (e.g. XFS)
sudo mkfs.xfs -L USBSTICK /dev/usb-vg/mydata
 
# mount 
sudo mount /dev/usb-vg/mydata /mnt

# umount
sudo umount /mnt

# deactivate logical volume
sudo lvchange -an usb-vg/mydata

# close LUKS partition
sudo cryptsetup close data

# eject drive
sudo eject /dev/sdb

Hope this helps.

./veracryp-..-setup-gtk3-gui

I get a (gtk) popup, which asks my pw,
I get an ok for uncompressing the installer
While the 2nd terminal just gives a "Press retun to exit"

That's all. No idea where I'm lost here..

I read some here in the forum, too. But I'm missing what the method for installation should be.
I didn't find it with apt, so according to the VeraCrypt website it leaves me with the tar.gz installation or deb-packages.

Has anyone experience to share on that?