Omg. Is this really where our society is at?

I don't have my own practice, and I suppose it shouldn't be an issue if you have built up a decent portfolio.

But I also look young  partly due to the curse and blessing of my asian genetics. Once I had a site super call me a kid during a site meeting. I had to tell him, Ok boomer, don't ever call me a kid again. He immediately stop talking and I never had a issue with him again afterwards. 

There is a good chance that you're right; with age comes experience, and for better or worse, potential clients will include their perception of your experience level in their decision making process. Are most of your potential clients older than you? How much older? What is the focus of your practice?

I've found that doing residential design there are some demographics I just don't do well with, and others that I do great with, so I focus more on the potential projects that are more likely to be successful. 

In a separate/prior career, I ran into a similar situation where  I was promoted through the ranks quicker than normal. The result was that I occupied a position of seniority while clearly looking quite young compared to those around me.

My solution was to literally grow out my facial hair more deliberately (yep, for real) - and it did work, the results were fairly obvious. Directly less questions to my authority/qualifications. And I really dislike having facial hair...

My experience is the inverse. I faced age discrimination as an employee or job seeker.

I was a mature student at college and after graduation several people would make unsolicited questions about my age and raise their eyebrows, either at work or during interviews, despite the evident high quality of my portfolio and skills (I was a first class degree graduate).

I don't know if I lost any positions as a result of this, but I made sure that I kept working very hard and disregarded the prejudiced people. 

In regards to your experience, I have heard junior architects complaining at times that they are not taken as seriously by contractors, due to their young age.

I have a similar issue.  I am on the younger end of my office.  I've been out of school and working professionally for over six years and licensed for almost 2 years.  I have had clients (of all ages and genders) ask me if I am the intern, where I go to school, when I graduate, if this is my first project, etc. A few contractors have tried to ignore me, and say they would rather speak with my boss (male, late 40s) until they realize I approve their pay apps.

I am a woman, so growing facial hair is out of the question (ha) I dress and speak professionally, but it doesn't seem to matter.  The main thing that has helped is focusing on what I gain from working with the good ones (colleagues, bosses, clients, and contractors) that treat me with respect and back me up when the situation requires it.  Just hustle harder and don't let them see you sweat.

We had an employee in their early 30's who had prematurely gray hair and beard.  Judging by the way people reacted to him, the combo of gray hair and good skin and relatively in-shape body is apparently the sweet spot.  People really listened to him, even in the company of much older and knowledgeable people from our firm.

Maybe consider dyeing in some gray into your hair.

Yes.  I started taking over the family architecture firm when I was 25.  Regularly faced it from both clients and project managers.  With the PM’s, it wasn’t hard.  I grew up in architecture, so I had decades of mentorship under my Dad.  They knew my experience and expertise and also knew I had a lot of training they didn’t in their backgrounds (like business stuff, contracts, etc.).  Answer question right that they didn’t know, and eventually they’ll respect what you know and no longer just see you as a stupid intern; be honest too if you don’t know btw and don’t bullshit your way through. 

With clientele, I cheated.  I brought a PM who was ten years my senior.  So, initial impressions weren’t a turnoff.  Once on board, I could prove myself and earn their trust. 

Another ‘trick’.  If you look young, they assume ‘cheap’ and unable to negotiate a contract.  I know how to negotiate so my fee structure looks cheap, but really isn’t Hint; percent of construction cost for arch only.  All consultants are cost plus.  Most just hear from their golfing buddies that architects run about 7% but fail to mention those fees normally include consultants.  So I’d be 5% and by the time you add consultant fees in back in plus coordination, you sat around 12%. Better yet is if there was zoning; that's hourly and basically would get you through DD before you even tapped your normal services fees; that'd put me in the 15 to 17% fee structure range.

The other ‘trick’ I’d use with my youth was building department waivers or getting them to interpret code my way.  Basically, I’d play inexperienced architect and put the reviewer in a ‘mentor’ role.  Then just ask the right questions like “what does this ‘exception’ mean?” or “what is the intent of that requirement?”, then lead them to my watering hole where those exceptions or that part of the code just doesn’t fit my design.

One though where I was stuck was in my expert witness litigation support I started taking on in my mid-30’s.  One firm pulled me in and told me flat out that while I did indeed have the knowledge and experience as well as concise accurate opinions and reports… A jury would judge my youth against the grey hair opposing expert and just believe the other guy more.  They told me they’d be happy to use me once I get grey hair and look the part.  Shit happens.  I still managed to keep them on for smaller cases.