Here is a sixth beta test for Teensyduino 1.54.

Install into a clean copy of Arduino if you previously installed beta3 or beta4.
SdFat-beta was renamed to SdFat. You may end up with conflicting duplicates if
installing over the top of beta3 or beta4.

Edit: Links removed. Please use 1.54-beta9

Changes since Teensyduino 1.54-beta5:

Fix multiple def with EEPROM put() & get()
Update FlexCAN_t4
Update NativeEthernet
Update RadioHead
Update ST7735_t3
Update SdFat to 2.0.5.beta1
Wire lib Scanner example updated
Audio waveform synth add bandwidth limited waveforms (Mark Tillotson)
Fix audio design tool conflict with DAC & PWM outputs (manicken)
Fix audio compile errors with Teensy LC (Frank B)
Add I2S output for Teensy LC (Frank B)
Add PT8211 output for Teensy LC (Frank B)
Add support for SGTL5000 in I2S master mode
Fix bug in SGTL5000 BiQaud filter calculation (Graham Whaley)
Fix minor bug in S/PDIF resampling (alex6679)
Add Play/Pause function to WAV player (standarddeviant)
Fix waveform synth discontinuities in phase modulation (Mark Tillotson)
Fix buzzing noise in FreeVerb due to numerical truncation (matt venn)
SGTL5000 support for switching headphones to input signal (Jurgen BeliŽn)
Add JavaScript version of wav2sketch (Matt Bradshaw)
Add LittleFS NAND & FRAM support (MJS513)
Add LittleFS LFSintegrity test program (Defragster)
Add OctoWS2811 RGBW LED support
Add OctoWS2811 VideoDisplay example for Teensy 4.x
USBHost_t36 add MassStorageDriver work-in-progress (wwatson)
USBHost_t36 Serial driver support for Teensy seremu (KurtE)
Update WS2812Serial for extra Teensy 4.1 pins
Improve serial emulation for non-serial USB types