[anyfactor]

He can do anything but getting a full time job.

What is even a job? It is just financial security. At your dad's age, is he really looking for that financial security of a job? On the flip side of things nobody would be comfortable hiring him as they might think, he might not fit in with the team or he has a higher possibility of quitting because young people could barely survive the grind.

Recruiters/employers are biased and they make binary decisions on first impressions. It would be brutal for him to be in a job first mindset.

Ask him to look into freelance work and cotract jobs. He might even be able to get some advantage because many people subsitute experience with age.

Or ask him to build something. The software industry is obsessed with the under 40 demography so he has insights to a niche that is untapped.