I agree with above: storing a seed phrase is a better option than storing a single private key, as it makes it easier to spend the coins in the future with less risk that you lose your change, and it also means you can avoid using a printer altogether and just hand write the seed phrase. Here is the process I would follow if I was going to do this today:
Use an old laptop which is permanently airgapped by physically removing the WiFi card.
Boot to a live OS from a USB stick (I would probably use Tails since I am familiar with it, but Ubuntu is fine provided it is a clean download and verified).
Download Ian Coleman's BIP39 site from GitHub here (
https://github.com/iancoleman/bip39/releases), verify it, and transfer it to the airgapped machine on another USB stick, SD card, etc.
Run it, generate your own entropy manually by flipping a coin or rolling some dice, enter the entropy in to the site, and write down the seed phrase by hand on two separate pieces of paper.
Generate a long and complex passphrase, either using a similar random process such as flipping a coin, or perhaps using an open-source password generator such as KeePass (again, transferred to the airgapped machine via a USB stick or similar).
Write this passphrase down by hand on two separate pieces of paper.
Enter your seed and passphrase in to the Ian Coleman site to generate a receiving address to send funds to.
Store the 4 pieces of paper securely and separately.