The government of Canada announced on April 26, 2022 that all lawful permanent residents of the United States who hold valid status in the country have been exempted from the electronic travel authorization (eTA).
To travel to Canada, these individuals do not need an eTA but must carry official proof of their status in the US as well as a valid passport from their country of nationality (such as a valid green card or a valid I-551 [ADIT] stamp in their passport).
All visa-exempt foreign nationals travelling to or transiting through Canada by air must apply for an eTA through the electronic system before entering Canada according to the Immigration and Refugee Protection Act (IRPA) and Immigration and Refugee Protection Regulations (IRPR).
Foreign nationals who hold any of the following documents below also require an eTA:
A passport or travel document issued by the Holy See
A national Israeli passport
A passport issued by the Hong Kong Special Administrative Region of the People’s Republic of China
A passport issued by the United Kingdom to a British national (overseas), such as a person born, naturalized or registered in Hong Kong
A passport issued by the United Kingdom to a British subject that contains the observation that the holder has the right of abode in the United Kingdom
An ordinary passport issued by the Ministry of Foreign Affairs in Taiwan that includes the personal identification number of the individual
Note that if a foreign national holding an eTA on the basis of eTA expansion eligibility is travelling to or transiting through Canada by a means other than air, they must have a valid Temporary Resident Visa (TRV).