My notes, things I have learned, and documentation I have created.

# fdisk /dev/sdb

# cryptsetup luksOpen /dev/sdb1 new_disk

# mkfs.ext4 /dev/mapper/new_disk
# mkdir /newdsk

Use the following to get the UUID for the partition/disk.
# blkid -s UUID -o value /dev/sdb1
# vi /etc/crypttab
…
new_disk UUID={result from blkid command above} none luks
…

# vi /etc/fstab
…
/dev/mapper/new_disk /newdsk ext4 defaults 0 2
…

# systemctl daemon-reload
# mount /newdsk

When you add a disk to a system that already has an encrypted disk, say the system disk, you will prompted twice for the passphrase. Once for each disk.

In Mint Linux 19.3, when you install xrdp, the dependencies are not automatically added. If you are having trouble with display (blank screen), you need to install the xorgxrdp, xorg-video-abi-23 and xserver-xorg-core packages as well.

# apt install xrdp xorgxrdp xorg-video-abi-23 xserver-xorg-core

I will update the post after trying in the latest version.