I'm also a literal greybeard (early 60s) on the east coast, and I haven't found this ageism to be a problem. Young companies are about "what can you do for me"

I'm also a literal greybeard (early 60s) on the east coast, and I haven't found this ageism to be a problem. Young companies are about "what can you do for me" and 40 years of experience gives me the intuition about architecture and implementation that you don't get without having lived through lots of failed projects! Also, with a long career, you probably have a number of significant successes under your belt, and, while past success does not guarantee future success, it appears that past failure is a strong indicator of future failure. New teams want people with a track record of success.