Epic Games agreed to provide free access to two of its shooters Unreal Gold and Unreal Tournament. Moreover, both games can be downloaded and installed on PC — they were saved in the Internet archive.
Both projects were removed from sale, but a group of Old Unreal enthusiasts managed to get permission from Epic Games to publish them in Archive.org. In addition, they made separate installers for Unreal Gold and Unreal Tournament, which automatically download .iso files from the server, allowing you to run them on PC without problems.
You can download the programs from this link and here. Most likely, both loaders will allow you to install mods for graphics and environments.
Earlier, another enthusiast ported Unreal Tournament from the first to the fifth version of the Unreal Engine 5.