cryptsetup open --type tcrypt /dev/sdb2 secrets
mount /dev/mapper/secrets /mnt/secrets

The first step creates the virtual partition (/dev/mapper/secrets) being the decryption of the real partition (/dev/sdb2), and the second step mounts that partition's filesystem on /mnt/secrets.

As per man page, if the VeraCrypt encryption has "personalized iteration count", you may need additional options to the open command.

Afaict tcplay does the same thing as cryptsetup, i.e. it creates that virtual partition for decrypted content access, and it doesn't mix in the filesystem mounting (which is an interpretation of the decrypted content).

But one thing I know for sure: Truecrypt is no more maintained for now about 12 years or so. So I am not astonished that Veracrypt is a bit more comfortable.

veracrypt --create /dev/sdb2

... to create an encrypted partition (it would then ask for a password),

and something like :

veracrypt --mount /dev/sdb2 /mnt/secrets

... to view the partition contents decrypted (it would then ask for a password)

and something like

veracrypt --dismount /mnt/secrets

... to unmount the partition

But tcplay seems completely different. Although creation seems to follow the same principle, the man page only talks of "mapping", not "mounting". The manual gives as example (ignoring hidden volumes and and non-default encryption options) :

tcplay --map=truecrypt1 --device=/dev/vn0

This presumably identifies the device (a partition) as an entity called "truecrypt1", but does nothing about mounting it on the file system.

The man page example goes on with :

losetup /dev/loop1 secvol --map = secv --device = /dev/loop1 
mount /dev/mapper/secv /mnt

How has this complexity arisen? What have loop devices got to do with it? It now takes three lines to mount an encrypted volume? Is this something of systemd's doing? I have a veracrypt encrypted partition from an earlier Chimera installation and I'm a bit reluctant to try mounting it with this new methodology in case it foobars it all.