Adobe does not offer "Adobe After Effects 2020" as a permanently free software. There are two primary ways to access it:
Many sites offering "Free Download" or "Cracked" versions of 17.0.5.16 often bundle malware or unstable "portable" versions. Pros and Cons (v17.0.5.16) After Effects 2020 (ver 17.5) download? - Adobe Community Adobe After Effects 2020 17.0.5.16 Free Download
For users with active subscriptions who need a specific older version (like 17.0.5) for plugin compatibility, Adobe's support chat is often the only official route to request an offline installer. Adobe does not offer "Adobe After Effects 2020"