Linux Mint 18.x reached the end of life
Clem Lefebvre, the head of the Linux Mint project, announced that the Linux Mint 18 series (18, 18.1, 18.2, and 18.3) has been officially reached EOL and will not receive any updates and technical support in the future. Linux Mint 18 was released five years ago and is based on Ubuntu 16.04 LTS, which will soon be EOL.
Clem Lefebvre provides two upgrade plans. One is to install Linux Mint 20.1, which is the latest version and will be updated until 2025. The other is to upgrade to Linux Mint 19.3, which is supported before 2023.
Since the 18.3 to 19 update is a major version upgrade, it will take more time. In addition, whether it is a new installation or a patch update, remember to back up the data so that it can be restored in time when a problem occurs.