Serial Monitor freezes on input when board doesn't clear RX buffer

I'm using an MKR1010 and am trying to run the SerialEvent example: https://www.arduino.cc/en/Tutorial/BuiltInExamples/SerialEvent

I recently updated to the 1.8.13 release a few days ago, and I'm trying to send characters using the serial port monitor as required in the serial even example. The serial port monitor it freezes up after a random number of characters - sometimes 1 sometimes 3. I haven't received any output over the serial port monitor as the sketch should provide.

EDIT: I came across this post on the element14 forums where someone mentions that serialEvent() can't be used with SAMD boards (https://www.element14.com/community/thread/74359/l/reading-uart-rx-buffer-mkr-wifi-1010-mkr-1000). There's no reason given - but can this be officially confirmed? I don't see it in the function's documentation: https://www.arduino.cc/reference/en/language/functions/communication/serial/serialevent/

Also - this might be a separate issue - the library manager is throwing Java concurrent execution errors when I try to open it.

Start with the linked SerialEvent example and serialEvent() reference, then reproduce the freeze on an MKR1010 using Arduino IDE 1.8.13. Determine whether serialEvent() is unsupported on SAMD boards and separately verify the reported Java library-manager error; done means the behavior is confirmed and the appropriate issue or documentation change is clearly identified.

Written by the indexing model from the issue text.