How can I save my old, important Whatsapp chat messages from automatic deletion when export doesn't go all the way back? So, I just scrolled all the way back in a couple of chats and found that the earliest available message was mid-conversation. Everything before that is gone. It seems Whatsapp has been silently deleting old messages. This is highly disturbing to me because the oldest period of messages available right now relate to the last months of my now-deceased mother. A lot of very important messages pertaining to that period are now gone!

Automatic backups to Google Drive have been on, but I just found that Google Drive won't let me download them on my own. The only options it gives me are to turn off the updates or delete the backup. It really pisses me off that Google gives Whatsapp more privilege to access my data than me.

I tried the export chat feature of Whatsapp, but it doesn't export everything. In my most important chat, I can scroll all the way back to September 2017, but the exported file only has from December 13, 2018, a week ago, onwards.

I tried the local backup, the Whatsapp directory in internal storage, but everything there is encrypted! What's it encrypted for, I wonder? So the user can't use it outside of Whatsapp! Great work Whatsapp team! I'm about to flip my bolted down desk!

It seems the only option available to me is to screenshot everything manually from last year onwards (that's gotta be thousands of messages to scroll through and screenshot), but I hope that someone here can give me a better idea to get the plaintext. I don't shy away from complex solutions, and though I'm not an Android developer, I am a programmer with a lot of Linux experience.
What I ended up doing is loading a chat on http://web.whatsapp.com and hit PgUp until I got to the oldest available post. It was seriously slow to load the whole chat. I could load the whole thing in the app in one or two minutes of swiping. In the Whatsapp Web, though, it took many hours. I had to leave a process sending PgUp keypresses to the browser window in a loop for the whole night. In the morning, then, I opened up the web-inspector, found the &lt;div&gt; that held all the chat's contents, right-clicked it, and selected "Copy Outer HTML". I pasted in a file, and that's it. That was in Firefox. I did the same thing in Chromium, just because, and found that Chromium does not copy the whole thing. It truncates :(. To get the whole contents of the tag, I had to select "Edit as HTML", put the text cursor inside the text field, hit Ctrl+a, and copy and paste to a file.

That covers the text, and blurred out previews of images (encoded in base64 in the HTML). The media (pictures, audios and videos) are accessible in the local backup unencrypted. I copied that directory elsewhere lest Whatsapp decided to overwrite it with a backup where it deleted important media.

That's apparently the easiest way to export a chat in Whatsapp. Maybe later, I'll provide instructions on how to cleanup what was pasted into something easier to read. The HTML is seriously ugly, though. There are no good class identifiers to easily restructure it to something more readable; they're all useless randomly generated  strings.