Hi,
Thanks for this helpful guide.
Unfortunately, it doesn’t work with my FP3+… Or i missed something.
The context: i realized some weeks ago that my FP3+ (bought in 2021 on /e/ os website, installation with the easy installer) didn’t propose me updates since the 1.19.1-s-20240109372023-stable-FP3 release (yes, it took me a long time to realize it 
). Even if i force the manual checking more than 20 times, even with advanced privacy on or off. And the App lounge can’t be able anymore to show, install or update apps, but it’s another problem (seen in some dedicated topics).
I followed advices on some topics on this forum, for example this current one, or Update from 1.19.1-s to 1.20-t on beyond2lte, or [HOWTO] an Unified Install Guide Project for /e/ steps 8 and 9 (english and french versions).
I tried to apply the dirty upgrade process by myself.
At first without computer, by recovery reboot.
there are multiple ways:
- download the file, go to " → settings → system updater" and use the called “locale update” feature if you have it in the “3 dot menu”.
I don’t have this menu…
OR
- download the file, boot the phone to the recovery mode and use “apply update” then “from internal storage” if your “recovery mode” have the feature.
OR
- download the file on a SDcard, boot the phone to the recovery mode and use “apply update” then “from External SDcard” if your “recovery mode” have the feature.
When I reboot in recovery mode, then select Apply Update, it doesn’t propose me neither “from internal storage” or “from External SDcard”. I have only “Apply from ADB”. I don’t understand why. Any idea?
OR
- download the file on a computer, boot the phone to the recovery mode and use “apply update” then “from ADB”
So, then I tried with ADB, installed on my linux mint 21.3 machine (fastboot too). The installation went well. I put the Debogage USB “on”, in dev options menu of my phone (i don’t know if it’s necessary, but in doubt…).
The command on the terminal adb devices returns one device (my FP3+ i guess), so it sounds good. I downloaded on my computer the last <file2.5>.zip for FP3.
When i launched the recovery reboot, then selected Apply update / Apply with ADB, the connection between my phone and my computer breaked down (a popup appears "Impossible de monter FP3 - Impossible d’ouvrir le périphérique MTP “003.021” " and on the terminal the command adb devices returns that my connected device is “unauthorized”.
And on my phone there is this error:
What did i missed?
I haven’t installed the Platform Tools. Maybe should i try to do with it? how can this change something?
I think i don’t have TWRP and it seems to me really harder to use… But could it be a solution?
If i understand well, there’s no need to do factory reset, and the loss of data would not occur by thy way, right? I’d rather not to have to do this.
Another question that i wonder: is that safe to update my FP3+ from 1.19 to 2.5? It’s a huge step!
I hope my message is clear. I’m not a developer, it’s a little difficult to me to do this by my own. Thanks in advance for help!