With this tool, you can:
Flashing is dead-simple. Hold the 'Download' button while powering-on the clock, or press the 'Reset' button while holding 'Download' button. Probably. Your clock may be different.
Reset without holding the 'Download' button and you can set up Wi-fi configuration, visit the device's WebUI, or add to Home Assistant. Then, click 'Connect' again.
If you are having issues seeing the option to setup Wi-fi configuration, try reloading this page. It doesn't matter which firmware is selected to send Wi-fi configuration.
These firmwares likely contain time zones that do not match yours. That's OK, you can change them! For non-HA versions, you can change the POSIX string of the Alternate Time Zone in the device's Web UI. For HA versions, you can override the time zones with Helpers.