The law to modernize nationality law (StARModG) was approved by the Bundestag on January 19, 2024. According to this, after the law comes into force on June 27, 2024, a retention permit will no longer be required in order to avoid the automatic loss of German citizenship if you accept Canadian or another citizenship upon application.
Attention: This only applies AFTER the regulation comes into force on June 27, 2024.
Until then, the previous regulation continues to apply: avoiding the loss of German citizenship only with permission to retain it. Further information on this can be found on the website of the Federal Office of Administration