It’s quite complicated. A lot of feature phones sold today have some smartphone capabilities, so exactly how much application-based tracking could be going on really depends on your device. Even in the best case scenario, a complete dumb phone could still be triangulated by cell towers. I can’t recall if that’s something done en mass but Michael Bazzell (in his podcast and maybe his book) details how easy it is to do even for those who aren’t law enforcement.
Then there’s the major downside to feature phones which is that they’re terrible for security. You can’t protect anything stored on it or anything sent to and from it. On the contrary, a de-Googled smartphone (ideally GrapheneOS but there are cheaper yet less secure alternatives) at least has some semblance of security as anything stored on or transmitted to/from the device can be encrypted. You also get the added benefit of being able to use it as an anonymous phone if you purchase the device and plan anonymously and exclusively use VoIP numbers. (Again, you can take it even further as discussed in the book.)
Whether it is “enough” depends on your threat model. I could see why you’d go for this setup so I won’t say not to, I just have 2 main notes:
- Just to reiterate, your setup with the feature phone isn’t ideal for privacy or security but if you struggle with avoiding social media apps on a smartphone I could understand why you’d have to resort to it.
- Installing apps like Signal over Waydroid potentially downgrades the security of your Signal communications. Mobile devices are generally much more secure than desktop devices and Waydroid in particular seems to be especially bad in regards to security. Whether you think you should be concerned about that is up to you, but if you decide to use a de-Googled (preferably GrapheneOS) phone in place of the feature phone, it’d probably be safer installing Signal there. (Of course you can still install their desktop app on Fedora for convenience.)