Ubuntu 22.04 LTS being a LTS comes with five years of standard support for Ubuntu Desktop, Ubuntu Server .. and three years for Ubuntu flavors like Ubuntu-MATE. That is expressed in release announcements, such as
Maintenance updates will be provided for 5 years from the initial 22.04 LTS release for Ubuntu Desktop, Ubuntu Server, Ubuntu Cloud, and Ubuntu Core. All the remaining flavours will be supported for 3 years. Additional security support is available with ESM (Expanded Security Maintenance).
If you enable ESM or Ubuntu Pro, those security updates will continue for a further 5 years, and can also be extended a further two if you add the optional legacy support; giving the potential for 12 years of support.
Ubuntu-MATE however being a flavor however, is fully supported for 3 years, so until 2025-April (ie. 3 years from initial launch in April 2022)
Your system will continue to receive updates after April 2025 as at its core, your Ubuntu MATE is a Ubuntu product, thus the Ubuntu packages get security fixes (packages from main) for 5 years, so you needn't really worry until 2027-April, but asking on sites like here, after MATE supports ends in April 2025 maybe uncouth.
I wrote about this recently on a support site; so I'll provide a link here; much the same detail using different words relating to 20.04 flavor that was EOL. Sites like askubuntu allow flavor support questions for the five years of standard support.