Yiimp is out of date; I've previously run this and found it difficult to get it to work. I suggest if you can make it work, you better switch to another open-source mining pool that works on modern systems.
I check the mining core; it seems it's also outdated. No one gives stars yet to this mining pool for me, I suggest try the other Yiimp version developed by the other community, like Yiimpool. This one has a script to automate install everything you don't need to set it up manually, the same as what you do with outdated Yiimp.
You can check the open source here:
https://github.com/afiniel/Yiimpoolv1It supports Ubuntu versions Ubuntu 25.04 and below.