May First has been using trac for 16 years and we are on the cusp of finally replacing it. Needless to say, I don’t recomment it.
It may be obvious to most, but when we started using Trac we didn’t fully realize how different bug tracking software and support software is - so be sure to focus on software designed for support.
We’re looking closely as Zammad. You can request a free trial via zammad.com which really helped with evaluation. We’re also looking at a Zammad derivitave called CDRL Link that focuses on security.
Would recommend it as a ticket system. After much research it seemed like the best solution. We have recommended it to charities and they seemed to enjoy it.
Also their team in Germany are very nice if you decide to host with them.