Look for communities or forums where developers discuss creating private servers for mobile games. Tools like apktool and dex2jar can be used for analyzing and modifying APK files.
Even if you get a v8.3 server running, you will realize something heartbreaking: You max everything in 2 hours. There is no clan war league pressure, no builder base progression, no capital peak. Nostalgia lasts 20 minutes.
For documentation purposes, here are the private servers that used to work with old versions. None are currently recommended, but they represent the history.
Revisiting the Past: Technical Functionality, Security Implications, and Preservation Challenges of Clash of Clans Private Servers for Legacy Versions
A developer-built software (like Supercell.Magic or Ultrapanda ) mimics the game's official communication protocols to process actions like upgrading buildings or training troops. Architecture of a Private Server