Dubbed Bionic Beaver, Ubuntu 18.04 LTS was released in April 2018 and it is supported by Canonical with software and security updates for at least five years.
But while Ubuntu itself receives this long-time support (LTS) of five years, the rest of the Ubuntu flavors only receive three years of support, which ended in May 2021. The last maintenance update for the Ubuntu 18.04 LTS (Bionic Beaver) series was Ubuntu 18.04.5 LTS, released in August 2020. From this moment on, there will be no further point releases published for the Bionic Beaver series, but Ubuntu itself will still receive regular updates that you can install via the software repositories.