As a 48 year old who lives in San Diego (so not Silicon Valley but geographically much closer than Europe) and still works as a programmer and who still enjoys coding and continually fights any attempt to put me into any sort of management role...
I think ageism is a valid concern but its also not a black and white issue because while I know quite a few older folks like me that are still constantly keeping up to date I've also known some people my age or just a little bit older who basically stagnated into irrelevance as experts in now discarded technology who never really moved on, so the line between what is ageism and what is people just not bringing value to the table anymore can be a bit blurry.
I'm by no means trying to suggest ageism isn't an issue in tech, I do see echoes of it when I look around and if I suddenly lost the network of people I work with, have worked with in the past, etc, who understand I'm still very technically 'flexible' for an older person I'm pretty sure it would make it difficult to find a job in the practical sense of getting pre-filtered out often just based on the age thing. So my heart really goes out to people who do find themselves in situations where they are capable but can't find work due to age primarily.
But, uh, the issue is somewhat complicated and very case by case, I think.