Flashing the Jolla C2

Is this flashing guide still recommended in March 2026?

I “bricked” my C2 with

  • charged up to 91%
  • switched on, went through the assistant (Wifi did not work) until the assistant either ended or I unintentionally swiped it away
  • was on the UI and looked around, found out I’m on 5.0.0. and the WLAN adapter “was not available”
  • did google this error message and found the advice to reboot the device
  • did reboot and now I’m stuck at the eternal spinner after entering the PIN

I looked into fastboot flashing: Fastboot flashing of Jolla C2
but when I run “fastboot getvar all” I get back an empty value which ChatGPT interprets as my fastboot loader being too old and that fastboot flashing wont be advisable.
Quick question here: Is ChatGPT right? If fastboot does not provide any variable, does this mean I still have the old (5.0.0.29 and before) bootloader installed on my phone?

Anyway, I’m now looking into this more low-level method. Is this method still advisable? I see that the mentioned ums9230_universal_unlock.zip archive has disappeared. From the file modification dates it seems that the ums9230_universal_unlock_EMMC.zip archive might be its successor. Is this correct?

I already opened an issue with Jolla, but it seems they are quite busy and maybe they want to see whether I can help myself before they offer me a send-in support.
Actually, I bought this phone in order to get in-depth hands-on experience with Sailfish OS, so I don’t mind the device bricking itself right out of the box. I just need some advice to work myself out of the hole.