LP048 checks whether all libraries mentioned in the depends field of library.properties exist in the Library Manager, however it is a warning and not an error.

The issue is that arduino-cli lib install will refuse to install any library whose dependencies are not in the Library Manager:

% arduino-cli lib install "OpenMV Arduino RPC"
Error installing OpenMV Arduino RPC: No valid dependencies solution found: dependency 'SoftwareSerial' is not available

I saw quite a few libraries mentioning built-in classes such as SoftwareSerial or EEPROM, which are not known to the Library Manager. When trying to install such libraries from the IDE 2.0, it will just refuse to install them without providing any error.

The easiest way to fix this asymmetry would probably be to raise this check to error level. Other fixes could be to implement ways to bypass this check at library installation time in CLI and IDE.

What do you think @per1234?