I'm in China and have to use that piece of crap. So here's how I locked it down:

1. Root your phone with Magisk. There's no way around it.
2. Install Storage Isolation (https://play.google.com/store/apps/details?id=moe.shizuku.redirectstorage) and deny access to all folders.
3. Install ApOps (https://play.google.com/store/apps/details?id=rikka.appops) and set pretty much everything to deny or ignore (ignore means the app receives the information "permission granted", but no data is provided, in case some permissions are "mandatory"). If you intend to use wechat to exchange voice messages or make video calls/send photos, the "use microphone" and "use camera" functions would be required. In a similar fashion the location access if you intend to use the location sharing feature.
4. Be acutely aware that wechat is not encrypting messages, neither end to end nor in the server communicaton. Everything you say can (and probably will) be read and archived. Don't say anything confidential or critical there.

And yeah really, try to convince your ~~wife~~ girlfriend to use signal instead. Or hell, even whatsapp is miles ahead.

My wife is Chinese as well, so even after we leave here she'll be using wechat to stay in touch with family, no way around it, but using messengers more commonplace in other countries is definitely better. Personally I will move wechat to another phone once we're out. For now that's not feasible as it's too much integrated into every function of life here.

Second phone just for WeChat.

Failing that use a android work profile and run WeChat inside of that. It should isolate WeChat from the rest of the days on your phone. WeChat would still have access to your location, microphone comment etc but not your data

To answer the question: GrapheneOS and a separate profile would be the safest but still...

If you are both outside of china there really is zero reason (other than preference) to use that piece of spyware.

You could sandbox it into a work profile that doesn't have access to your main profile. Storage is completely segregated, and the work profile can be easily disabled when you're not using it.

The best solution is obviously to choose another platform and convince your girlfriend to use that, explaining how this little extra effort on her part to use another app goes a long way with you in terms of appreciation and understanding of a partner's boundaries and comfort zone.

FWIW, WeChat and 微信 are different apps. With a non-Chinese phone number and Google Play Store download, you'll be using the international one (WeChat) instead of the Chinese one (微信). There are still privacy concerns, but it'll be less invasive than what you'd have with the version that people in China are buying their groceries with and stuff.

I'm sorry I don't have advice for how to actually protect yourself, though... I'll be keeping an eye on this thread to see what I can learn.

I stopped using every messenger besides signal and Matrix. Even my not tech savy parents are using signal now - its in my opinion the better solution to stand your ground and may push others into using the better apps

If you really want to isolate it, grapheneOS lets you put it in its own profile almost totally isolated from anything in any other profile.

But you probably don't want to buy a g! Pixel.

You could buy a separate phone and only run that app on it. Hassle but it would be secure.

Maybe get a girlfriend that isn't a brain washed spy? \s

Just use a different app then? You don't need to come up with some high tech solution. She won't use that anyway. But something simple like signal should be sufficient.

Brace yourself for a weird recommendation:

Don’t worry about it or switch to ios.

You’re on a different marketplace for phone apps than chinese nationals so you’re not getting the same wechat as they are. If you trust your platforms marketplace and your phones security and privacy tools then just don’t worry about it and use them like a normal person.

If you don’t trust your platforms marketplace or security and privacy tools, switch platforms.

It doesn’t seem from your responses in this thread that you’re in a good spot right now to learn everything required to root and run an alternative os securely and act as your own security auditor. Not a value judgement, I’m not in a position to act as my own diesel mechanic. That’s why I said maybe switch to ios if you feel exposed by stock android instead of saying you ought to try to navigate the alternate os/custom rom world.

It might seem like some people in the replies have given good walkthroughs, and they definitely have, but at some point you’re gonna have to make a decision about something that either isn’t documented on a wiki or no one responds to questions about.

Maybe the best choice is to either not worry about it or switch platforms and no matter what you choose, put the phones security and privacy tools to use and be more considered and self aware about how you use your phone.

E: Jesus Christ. Some of the responses you’ve gotten are astonishing. Maybe ask in hexbear or something just to get an alternative view.

If you are serious with this relationship (or you expect to still have Chinese partners in the future), I strongly recommend you buy a separate device for all the Chinese spywares required to maintain communication with your partner(s). At some point you will have to enter China, and it is best that you take only this device with you into it then.