I've been testing and using this Python IRCd which much success, something that might have sounded crazy awhile ago, but has good performance and features (including IRCv3). Below is some of the information from the author/creator, Y4kuzi, along with additional links and a network that you can view it running, with services linked and other servers as well.

If you want to test it out, feel free to jump on my IRC network and give it a shot; irc.ChatNPlay.org

GitHub: https://github.com/provisionircd/ProvisionIRCd

A modern IRCd written in Python 3.10. Support for lower versions has officially been dropped.
Massive code overhaul, so there might still be some issues.

Very modular, all modules can be reloaded on the fly (not always recommended)
IRCv3 features
Full TLS support
Extended channel and server bans
Linking capabilities
Flexible oper permissions system