Here is a first beta test for Teensyduino 1.43.

Old beta download links removed. Please use the latest version:

Changes since Teensyduino 1.42

Support for Arduino 1.8.6
Ethernet updated to 2.0.0
Fix default Ethernet CS pins on Teensy 2.0 & Teensy++ 2.0
Fix USB Keyboard '#' for UK & Irish layouts
Generic UDP class support beginMulticast
Fix USB MIDI hogging transmit buffers
Fix FreqCount for use at high frequencies
Installer automated install, use --dir=<directory>