Google announced this morning that it will stop indexing content within Adobe Flash files, SWF files, this year. Google said "Google Search will stop supporting Flash later this year. In Web pages that contain Flash content, Google Search will ignore the Flash content. Google Search will stop indexing standalone SWF files."
Google first started to index some Flash files back in July 2008, which was over 11 years ago. But since Flash is disabled by default in Chrome (starting in version 76), Microsoft Edge, and FireFox 69 and Safari - Google will stop indexing it.
Google said "Most users and websites won't see any impact from this change."
Google said with HTML5 there are good alternatives, standards even, that you can use to accomplish similar things.
As an FYI, Google never really indexed or ranked Flash content that well.
Update: John Mueller of Google did clarify that Google didn't really index full Flash sites anyway:
Viking Kittens is on YouTube now, so I think it's fine.
— 🍌 John 🍌 (@JohnMu) October 28, 2019
Anyway, this is specific to textual content / full sites that are in Flash; videos & animations generally wouldn't be indexed in web-search anyway.
Forum discussion at Twitter.