The tools work in the local network or over the Internet, and the firmware needs to support PlatformIO OTA update mechanism with the code having the line ArduinoOTA.begin();
If your ESP8266 device is already running such firmware, you just need to load the new firmware in the program, input the IP address and port, and click flash.
Jochen programmed BitBumper ESP8266 Flash with Lazarus/Pascal, but as not released the source code at this stage. Instead he shared FlashEsp8266.exe tools for Windows as a freeware program, as well as user and developer documentation here. If somebody needs this tool for Linux, Jochen can build it and release to you as well.
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