@peter-gamma I think you've been told that you can't use Veracrypt on Ut and encrypt it, nothing you can do on your mobile.
There is one thing you can do yourself, if it is so important for you to encrypt a micro SD, I see that you want to have information and not share it in case you lose it.
I suppose you want to use the micro SD inside your phone, either Android or Ubuntu touch, well you can have Veracrypt, but not use it from the phone,
is the same option as if you want to use an operating system on a micro SD,
With this you will see how to put an operating system in a micro SD that you then put in your phone,
IMPORTANT: watch how the partitions are made, do it the same way and add a partition at the end of the microSD in fat32 for use only with Veracrypt, use a 128Gbs micro SD.
The good thing about this is that you have your Linux operating system with you, the Veracrypt partition added and a partition that uses your mobile.
You will be able to carry it in your micro SD but use it from your PC or from the operating system you have installed in your microSD.
I'm sending you a link not to extend myself, I hope this option is worth it for you, in my case I use LUKS Encription from Ubuntu Mate 20.04.