How can I check to verify my Ubuntu MATE OS is encrypted?

[ouroumov]

More or less, yes.
See here for more info:

Installing Ubuntu with Full Disk Encryption

Background Encrypting your hard drive is the only decent counter measure against someone gaining physical access to your computer. Encrypting your hard drive does not protect you from malware ex-filtrating your data while your computer is being used. Full disk encryption is different from home folder encryption in that an attacker that gains access to your computer cannot plant malware into the operating system. Home folder encryption does not protect you from that kind of attack since only your…