We don't run Solr. We can't test it, so we can't maintain it. It may be broken already.
Last time I proposed to drop it, there was one use who reported using it.
I think a fair solution would be to drop SolrTTMServer from Translate, and make sure that if anyone is willing to maintain it, they can do so in a separate extension.
A first step would be to deprecate it loudly.