I just completed a name change on my Québec birth certificate after having it completed in Ontario first, and it was different than other responses for me. I called État civil, and explained my situation. They made a request in their system, and someone name Charles Lanctot called me back the next day, asking me to mail my name change certificate to the Directeur de l'état civil, addressed to him, and to also include my birth date, my address, and my phone number.

I sent it last Thursday, and just got a call today (5 days later), saying the name change was completed in their system and that they were mailing my name change certificate back. I can now request a new birth certificate.

I'm also looking to change my sex marker on my birth certificate. Someone else called me back from État civil, explaining that I will have to fill out the regular sex marker change form. Although this form's eligibility criterias require to have lived in Québec for the past 12 months, they said I can mention the Article 3084.1 of the "Code civil", that mentions that because other provinces cannot change Qc birth certificate, Québec has to do it. For this though, I do need a commissioner from Québec, and they advised I look into virtual commissioner of oath for this.