Because this is an older version, it is no longer the primary download on the main Thunderbird website. To ensure a safe, malware-free installation, use these verified sources: Version 78.14.0 - Release Notes — Thunderbird

was a milestone release in the Extended Support Release (ESR) cycle, serving as one of the final stable versions of the 78.x branch. Users often seek this specific version to maintain compatibility with older operating systems or legacy workflows that were altered in later "Supernova" redesigns. Where to Download Thunderbird 78.14.0 Safely