SoftwareSerial.h not found (suddenly)

Development Tools IDE 1.x
1

Arduiono 1.8.19. Arduiono Nano. Platform macOS (Bigsur)

I had a project working using SoftwareSerial.h
Today I startup the project again (which had worked last time flawlessly) and I'm getting

exit status 1
SoftwareSerial.h: No such file or directory

Things I did in the meantime was to install the Arduiono 2.0 IDE. And decided to remove it again from the system. Maybe I wiped out the library with it?
Not sure though. Maybe I inadvertently deleted a directory in the course of freeing up space.

Also my setting (board) look screwed. Maybe I messed up the board settings. But how do I get back to the right settings for the Arduino Nano?

2

I solved it. Installed the MegaAVR boards from the Library Manager, chose Board Arduino Nano, and the project compiled again. This option wan't there before. So I must have deleted it. Thanks.

3

Just a hint: never use installer (i.e. no need to "uninstall" anything), always use "portable" manual installation from ZIP file downloadable from the site.

4

Great that you solved it.

Which option?

5

The solution does not make sense, because the megaAVR boards package is not used with the classic atmega328 based nano.

6

The Arduino Nano option in the Board menu.

Maybe I installed also Mbed OS or something that brought the SoftwareSerial library back.

7

As @david_2018, said, it did not make sense. But you might be right that your action did put the missing library back.

You could probably have downgraded the AVR board package as well and next upgraded to the version that you did use before.