Print out a tabular sheet of
Website name | account name | password | Date last changed | Notes (check qs and additional login info)
Paper is safer imho. I'd love to take him to a password store but he's ipad and integrations are poor. The built in Keystore is fine: he just forgets which ones he's reused. Chrome does good checks if you love Google.
2FA needed. I wish it wasn't SIM/txt but for now it's all I can reliably get him to apart from Apple "check trusted device"
Distinct pw per account is increasingly vital. Seniors have shitloads of risk in their pension banking and related.