If you specifically need the 2018 version (for instance, to match a specific system or project requirement), your options are limited:
: Choose between individual, business, or student/teacher options.
However, you can still access After Effects for free via a trial of the current version or explore alternative ways to find older installers. Official Free Trial (Current Version)
: Download and install the Creative Cloud Desktop app, sign in, and select "Install" for After Effects. Accessing CC 2018 (Legacy Version)
: If you are part of an organization or school, your IT administrator may have access to older installer packages via the Adobe Admin Console. Learning Resources for CC 2018