Q2A supports tags out of the box, so technically you don't need an extra plugin. However, you may want to get some additional plugins anyway, specifically Advanced Tag Descriptions (because the builtin description handling is kinda bare bones) and Tagging Tools (for better manageability).
The minimum an maximum number of tags allowed for a question is configured under Admin → Posting.
Welcome to the Q&A site for Question2Answer.
If you have a question about Q2A, please ask here, in English.
To report a bug, please create a new issue on Github or ask a question here with the bug tag.
If you just want to try Q2A, please use the demo site.
April 20, 2021: Q2A 1.8.6 released!