Some tips for using Teensy on linux:

The teensy board support package is only supported in the Arduino applications downloaded directly from the arduino site, NOT on versions distributed by package managers. I used the AppImage and it worked fine. If you try to install the teensy board package on an unsupported version of Arduino you might see errors like “archive not supported”.

Even when you have a supported version of Arduino installed, installing the Teensy board package isn’t totally reliable. The first time I downloaded it, compiling would fail with the following error:

fork/exec /home/barnaby/.arduino15/packages/teensy/tools/teensy-compile/11.3.1/arm/bin/arm-none-eabi-g++: no such file or directory

Compilation error: fork/exec /home/barnaby/.arduino15/packages/teensy/tools/teensy-compile/11.3.1/arm/bin/arm-none-eabi-g++: no such file or directory

The 11.3.1 folder existed, but was empty. Down- then upgrading the board package didn‘t fix it. Removing the board package and reinstalling it did work.