I have written before that I'm a DSL customer of the German ISP M-Net with a FritzBox 7430 as router. The router is managed by M-Net and they removed the possibility to update it by myself in the user interface. However, M-Net was lagging behind and used the outdated version 7.12 (August 2019) in October 2020.

I found a simple workaround which gives you the possibility to update your FritzBox without asking the hotline. I have used this workaround to upgrade to the latest version 7.21 which has the new cool security features WPA3 and DNS-over-TLS. Here is how I did it:

• Download the latest firmware image from the vendor AVM.
• Export the current configuration of your Fritz!Box.
• Unplug the WAN cable (DSL connection).
• Reset the Fritz!Box to the factory settings and reboot it.
• Log into the web interface and ignore all warnings about the missing DSL connection. Now, you are able to access the "System Update" functionality.
• Flash the update and reboot again.
• Reconnect the WAN cable.
• M-Net will redeploy your configuration (and remove your functionality).

I do not know if this is intended, so use at your own risk.