A YouTuber and Portal speedrunner named nicl83 has discovered that the version of Steam included on DVD versions of Half-Life 2 can still be recognized by Valve's servers and updated to the modern client.
However, there are some limitations, as updating the client deletes the archived version of Steam and the process is time consuming and complex. Nicl83 had to use a Windows XP VM to partially update Steam before he could transfer it to a Windows 7 VM to complete the update and log into his account.
Impressive Compatibility in a World of Obsolescence
The fact that this prehistoric version of the client is still compatible with the modern servers is impressive in a world where technology quickly becomes obsolete and is replaced by newer models.