iirc, twitter turned off all anonymous access, unless you come from a search engine, then you get a limit number of requests. So zedeus came up with an idea to make a massive pool of search engine'd api tokens and use those to keep nitter up. The mirrors would have to copy that idea, and few (0?) have atm.
The current state is to use guest accounts [1]. If you use that branch instead of master and get a collection of accounts, you can run your own instance. For my personal use instance this is working fine with the initial set of accounts I put in. No idea how long this will work and/or when it is going to get merged, it is a moving target.
I think the token workaround you mentioned is the old way that no longer works, but I am not sure.
