What template do you refer to.
Debug and solve the errors, thats what I do whenever I use someone elses example code.
Sounds like you might be using the developer rig which has a handful of weird issues and generally best avoided especailly when using “seed my project with example code”.
You can fetch those examples from the TwitchDev Github manually and do whatever npm tasks you need. Repos: Twitch Developers · GitHub Sure some of them are a little outdated, but they are just examples
Based on your other post you already have a working extension via a nextJS project, no?