Also if train ferries are allowed (across Lake Van in Turkey) there could then even be a non-Russia world's longest train journey - if Mashdad-Merv opens https://tvbrics.com/en/news/iran-and-turkmenistan-to-launch-first-passenger-train/
The only issue?
Instead of Russia, you have to cross Iran 🇮🇷 and Turkmenistan 🇹🇲
No visa headaches there, oh no!