Etcher copies images to drives byte by byte, without doing any transformation to the final device, which means images that require special treatment to be made bootable, like Windows images, will not work out of the box. In these cases, the general advice is to use software specific to those kind of images, usually available from the image publishers themselves. You can find more information here.

Some programs, usually oriented at making GNU/Linux live USB drives, include an option to set persistent storage. This is currently not supported by Etcher, so if you require this functionality, we advise to fallback to UNetbootin.

This is a feature provided by AppImages, where the applications prompts the user to automatically register a desktop shortcut to easily access the application. Follow the steps you can find here

Ubuntu images (and potentially some other related GNU/Linux distributions) have a peculiar format that allows the image to boot without any further modification from both CDs and USB drives.
A consequence of this enhancement is that some programs, like parted get confused about the drive's format and partition table, printing warnings such as:
/dev/xxx contains GPT signatures, indicating that it has a GPT table. However, it does not have a valid fake msdos partition table, as it should. Perhaps it was corrupted -- possibly by a program that doesn't understand GPT partition tables. Or perhaps you deleted the GPT table, and are now using an msdos partition table. Is this a GPT partition table? Both the primary and backup GPT tables are corrupt. Try making a fresh table, and using Parted's rescue feature to recover partitions.
Warning: The driver descriptor says the physical block size is 2048 bytes, but Linux says it is 512 bytes.
All these warnings are safe to ignore, and your drive should be able to boot without any problems.
Refer to the following message from Ubuntu's mailing list if you want to learn more.

Electron is based on Gtk2, which can't run natively on Wayland. Fortunately, the XWayland Server provides backwards compatibility to run any X client on Wayland, including Etcher.
This usually works out of the box on mainstream GNU/Linux distributions that properly support Wayland. If it doesn't, make sure the xwayland.so module is being loaded by declaring it in your weston.ini:

[core]

modules=xwayland.so

This entry aims to provide an up to date list of runtime dependencies needed to run Etcher on a GNU/Linux system.

You can set the ETCHER_FAKE_S3_LATEST_VERSION environment variable to a valid semver version (greater than the current version) to trick the application into thinking that what you put there is the latest available version, therefore causing the update notification dialog to be presented at startup.
Note that the value of the variable will be ignored if it doesn't match the release type of the current application version. For example, setting the variable to a production version (e.g. ETCHER_FAKE_S3_LATEST_VERSION=2.0.0) will be ignored if you're running a snapshot build, and vice-versa.
See PUBLISHING.md for more details about release types.

Sometimes, things might go wrong, and you end up with a half-flashed drive that is unusable by your operating systems, and common graphical tools might even refuse to get it back to a normal state.
To solve these kinds of problems, we've collected a list of fail-proof methods to completely erase your drive in major operating systems.

Etcher requires an available polkit authentication agent in your system in order to show a secure password prompt dialog to perform elevation. Make sure you have one installed for the desktop environment of your choice.

Etcher GUI is based on the Electron framework, which only supports macOS 10.10 and newer versions.