You do realize that Ubuntu MATE being a flavor of Ubuntu comes with 3 years of supported life.
The release announcements for Ubuntu 18.04 state
Maintenance updates will be provided for 5 years for Ubuntu Desktop, Ubuntu Server, Ubuntu Cloud, and Ubuntu Base. All the remaining flavours will be supported for 3 years.
Ubuntu MATE announced the end of 18.04's support cycle on this site too, ie. see Ubuntu MATE 18.04 LTS reaches end of life