Well you could try what I may/may not do
Download the crypto's wallet, and then verify the file hash (There really should be one provided, otherwise the devs dont know how to make a damn wallet) {hopefully it's a bitcoin-core clone or something along those lines}
Boot into a (
securely installed - So verify the hash, of the ISO.) live Ubuntu USB and open the wallet offline (Unless there isn't a linux wallet, in which case you do a fresh install without internet), and then generate a private key for a receiving address.
Now you want to securely store this private key. I don't use the most secure method, but I find it gives me peace of mind. (I've lost way too many loaded wallets on my phone after doing a factory reset without backups)
I manually copy down each letter of the private key onto my web-connected PC, and after every couple of letters, I type a space and a random word. Then I continue typing a couple more letters, then another random word. Repeat. This prevents malware on your computer that detect strings that look like private keys, not realise that you're typing a private key (I hope). Then you encrypt this string of text using openssl or pgp, whatever you want. I just use my own PGP key.
I then take this encrypted block, and email it to myself. My email is then protected with 3fa.
It's not the most efficient, nor most secure, but that's what I currently use.
But then again, most malware/hackers only care for large cryptocurrencies or at worst, ERC-20 tokens (ew). I doubt they'll go for your random cryptos.