There is no automated uninstaller.
You have to remove Eclipse manually. At least Eclipse does not write anything in the system registry, so deleting some directories and files is enough.
Note: I use Unix style paths in this answer but the locations should be the same on Windows or Unix systems, so ~ refers to the user home directory even on Windows.
According to this discussion about uninstalling Eclipse, the reasoning for not providing an uninstaller is that the Eclipse installer is supposed to just automate a few tasks that in the past had to be done manually (like downloading and extracting Eclipse and adding shortcuts), so they also can be undone manually. There is no entry in "Programs and Features" because the installer does not register anything in the system registry.
Just delete the Eclipse directory and any desktop and start menu shortcuts and be done with it, if you don't mind a few leftover files.
In my opinion this is generally enough and I would stop here, because multiple Eclipse installations can share some files and you don't accidentally want to delete those shared files. You also keep all your projects.
If you really want to remove Eclipse without leaving any traces, you have to manually delete
~/eclipse/photon/)The installer has a "Bundle Pools" menu entry which lists the locations of all bundle pools. If you have other Eclipse installations on your system you can use the "Cleanup Agent" to clean up unused bundles. If you don't have any other Eclipse installations you can delete the whole bundle pool directory instead (by default ~/p2/).
If you want to completely remove the Eclipse installer too, delete the installer's executable and the ~/.eclipse/ directory.
Depending on what kind of work you did with Eclipse, there can be more directories that you may want to delete. If you used Maven, then ~/.m2/ contains the Maven cache and settings (shared with Maven CLI and other IDEs). If you develop Eclipse plugins, then there might be JUnit workspaces from test runs, next to you Eclipse workspace. Likewise other build tools and development environments used in Eclipse could have created similar directories.
If you want to delete your projects and workspace metadata, you have to delete your workspace(s). The default workspace location is ´~/workspace/´. You can also search for the .metadata directory to get all Eclipse workspaces on your machine.
If you are working with Git projects, these are generally not saved in the workspace but in the ~/git/ directory.