Hi. I'm using unofficial rom of the newest LineageOS for my Xiaomi Redmi Note 12S. I know it's not that secure to use unofficial rom as using official one because it might have malware but I think that I trust guy behind a rom and I even donated him for his hard work. Official firmware for Xiaomi is terrible and had a lot of spyware, I couldn't sleep with awareness of this.

For right now I'm planning to make my phone more private and secure. I heard that SIM Card is really big privacy issue and it can take control over device. I'm planning to don't using SIM Card on my main device and instead put in my old IPhone 7, then I will share internet from it or make calls if I will have to. I don't trust Apple too much but I think that their system is much better hardened than android when it comes to stuff like that. I don't planning to put any important stuff on IPhone, expect for proprietary software like banking apps etc. I think that ICloud account is huge privacy issue but I think that solution is better than what I have right now. So I'll have FOSS software only on my main Xiaomi Phone.

Then maybe I should root my LineageOS to harden it? It will give more control over my device and I could control it network traffic by firewall, add additional encryption if it's possible etc. What solutions can you recommend? Also I heard that opened bootloader is security issue but to be honest if I was able to do this by exploit avoiding doing this by manufacturer way I think that cops or hackers can do the same if they I will get my phone.

What can I do also for more privacy and security? I think that I should use work profile and private space which are great solutions. Also I can make some faraday cage which will also dull a sounds from environment, avoid holding sensitive data on my phone and have different accounts for messengers.

What do you think about this? How are you using your phone and what can you recommend for privacy?