[key] does not (on my ubuntu laptop) receive either '{' or '}' (ascii 123 or 125)

'[' and ']' -- yes. All other keys I'd expect, yes. But with the shift key down, nothing from those same two particular keys.

This is only a problem in the extreme high register of a text-keyboard organ but... it puzzles me a lot!

@forrest Unfortunately, for your application, ascii 123 and 125 are reserved characters in Pd. You will find that ascii 92 is not working either.
You will see a message in the Pd terminal that they have been "dropped".
You will be able to use those physical keys if you remap them in Ubuntu to another character....... if there are any others that do not now exist on your keyboard.........
David.

Thanks. Maybe will remap 123 & 125... or switch to a different assignment of notes to keys, ie instead of zxcv being notes c d e f, have zxcvb => c d e f g. Four octaves instead of five, but that's 8 octaves with the caps lock.