So, I've decided to try and do some analysis on my WhatsApp chat history. For that purpose, the built-in export function would work quite well, but it is for some reason restricted to the latest 40.000 messages. Some of my chats go back way further than that, and I'd like to include those conversations in my dataset.
And that's where it gets complicated. Things I've tried so far:
A variety of recovery tools (drfone, BackupToolForWhatsApp,...) that invariably failed to connect and/or demanded a lot of money and/or contained malware
Finding the msgstore.db.crypt12 as a file on the phone and opening it as text with various apps (some people claimed that worked, it didn't though, everything just crashed or complained about the format)
Copying the msgstore.db.crypt12 onto my computer and there decrypting it with the key file, which led to the next problem, obtaining said key file.
A bunch of outdated and thus no longer functional WhatsApp key extractor tools which tried to either grab the backups off Google Drive, or temporarily install a legacy Version of WhatsApp with a vulnerability that allowed the key to be extracted. This failed because the tools haven't been updated in like three years and I'm not Java-savy enough to go digging in their source code myself. I actually downloaded a legacy APK to try and manually install that old WhatsApp version, but that only led to an error about the datetime of my phone (which was set to automatic and thus was correct) and no key.
Rooting my phone in order to get access to the directory where the key is hopefully located. This failed, perhaps because I did the mistake of updating my firmware to the July 2019 patch level, and so no root exploits seemed to work
Digging around in protected directories with tools that do not quite require root access. However, I wasn't able to locate anything that even looked like the place WhatsApp might store its key.
Reading through lots of forum posts on the same issue without any discernible results.
I'm using a Samsung Galaxy S8, model number SM-G950F, German localization, with Android 9.
My question is simple: What else can I do? It can't be that it's literally impossible to dig at the messages which WhatsApp is happily storing and backing up. I'd even be willing to buy some software as long as it's reasonably priced and guaranteed to work.
Also, what directory would I be looking for to get that key, assuming I'd somehow get root access?
Update 28.07.2020: It seems that in some locales (specifically the EU?), the native export function was disabled in its entirety. The method detailed in my answer below still works excellently, however.