Hi all. I'm one of the maintainers from opentelemetry-php, how can I help here? tbachert/spi is a package developed by one of the opentelemetry-php core contributors which we have started to use to configure parts of opentelemetry. I guess think of it as dependency injection, based on configuration in composer.json - the reason for the plugin is to compile/generate an output file of SDK dependencies.
Right now, opentelemetry should work just fine with that plugin disabled (it's currently only used by a new declarative configuration feature that's still being actively developed).