Error on an old phone, can't get the list of apps, likely a certification issue. How to solve?

1

Long story short. I have an old smartphone device which I would like to set up as a webserver or ftp server. I tried postmarket os, and basically bricked the device. After too much tears I managed to flash the original chinese rom into it. (EU is impossible to find)

Device is a Mi 4s, and now has a chinese rom with android 7.0 from November 2018.

So I installed F-droid into it, but it does not show or find any app. I have managed to screenshot an error given:
F-Droid : F-Droid: java.security.cert.CertPathValidatorException: Trust anchor for certification path not found. java.security.cert.CertPathValidatorException: Trust anchor for certification path not found.

So far it looks like a certification issue. Now the questions. Can it be solved? I have found other topics about similar certificate issues, but I have not managed to solve my problem with the topic solutions.

Any way, I am stuck, so any help would be appreciated.

Screenshot_2025-07-26-20-02-08-277_org.fdroid.fdroid
Screenshot_2025-07-26-20-02-08-277_org.fdroid.fdroid1080×1920 110 KB

2

Retry until it gets a good mirror.

Try to add the cert too: Running on old Android versions | F-Droid - Free and Open Source Android App Repository

3

I had to install this pem (downloading, changing extension and passing through bluetooth) https://letsencrypt.org/certs/isrgrootx1.pem.txt

This chinese ROM does not allow to install in Android OS Settings > Security > Install Certificates From Storage as per the website instructions, but you can install in Android OS > Options> WLAN> Additional Options, and then instead for WLAN select something like VPN and Apps.

It did the trick, and it does work now. Thank you.

4

If this is about F-Droid getting stuck and/or taking a long time on “Updating repositories” I have the same issue. I’ve tried clearing cache, force stopping the app, disabling and re-enabling repositories and restarting my device.
F-Droid 1.23.1
Android 7
Samsung SM-J730F

5

Read above Error on an old phone, can't get the list of apps, likely a certification issue. How to solve? - #2 by Licaon_Kter add the certificate, restart device, retry