Paper. There’s a project called paperkey that allows you to store GPG keys on A4 paper. You could apply a similar approach to your age encrypted private keys or store them in plain text.
Modern smartphones have excellent OCR (optical character recognition) capabilities, so converting images of printed text back into digital form is now quite easy and reliable.
Personally, I use 1Password, and even they recommend printing out a PDF copy of your passwords and storing it in a secure location - like a physical vault. It’s a practical backup in case something happens and someone needs access to your credentials.
Side-note because a friend went through it.. if you are going through a divorce or about to begin divorce procedures, burn that list :)
Your soon-to-be ex-wife will try to get her hands to all these passwords because: 1) she 'will prove' by reading all your emails that you <verb of doing something wrong>, 2) she 'will prove' that you hide money/assets/etc. (because why do you have an account on Bank/Broker XYZ and never told her?), 3) why did you buy flowers from "BuyYourWomanFlowers.com" 4) use your imagination for worse.. anything that can be used against you, will be used against you.