My wife and I used to run RCIA for teens/young adults. Something I always mentioned to our candidates getting confirmed is that in some Eastern Rites, people get confirmed at the same time they they are baptized (as babies or very young children), because it serves as an important reminder that Confirmation provides a tangible spiritual benefit to those who receive it, which is a tremendous positive for those who celebrate Eastern Rite practices.
In the West, there’s an association where the idea of the recipients of Confirmation are making the choice for themselves, so they need to be of a certain age. This has a practical benefit of allowing people to make the choice to receive it themselves, so there’s a tangible memory present.
Since we are in the Western Church, so it’s the local ordinary who makes such decisions. In most cases, that’s the local Bishop who decides the appropriate ages. This discretion actually goes beyond Confirmation - in my diocese, the Bishop set guidelines for when men can become a deacon (youngest child must be 16 at the time of ordination). For the priesthood there’s certain criteria as well. Father Z was kind enough to provide applicable Canon Law references, and I totally agree with his interpretation of them. So if someone came to me asking for advice on this, I would echo what Father Z said ;talk to your bishop or his delegates and ask for an exception. Explain the situation, I’m sure reasonable heads will prevail. If they do not, then discern looking at other territorial authorities which could be an option.
Regarding the SSPX, it might sound enticing, however you need to keep in mind it wasn’t but two years or so ago that their Marriages, and Confessions were invalid due to not having faculties, and if Confirmation requires faculties, then those were invalid as well. So far as I know, Pope Francis’ giving them faculties to perform Sacraments during the year of Mercy was extended - however you need to take a hard look as to why they were in that position in the first place. To some, people are sympathetic to the SSPX and their current position. To others such as myself, although we understand their position and believe it’s possible that people within the Church could have handled the situation better, I fundamentally disagree with how the SSPX handled things - from the trying to fast-track the Society’s recognition as a Society, to the breaking of Canon Law of the unauthorized consecration of Bishops, to the refusal to accept the very generous offers over the years coming from the Office of Kephas and his approved delegates.
So in essence, assuming that Pope Francis’ incredibly merciful gesture is still applicable, yes you can technically go to the SSPX and receive Confirmation. But by doing so you are going to a disobedient group because you don’t like the policies your Bishop put into place, which places yourself in a position of disobedience - that’s not a good look, nor is it necessarily setting a good example. For those reasons, in this circumstance, I would avoid going to the SSPX chapel.
I wrote a lot more about this, but man, 3200 character is nothing.