Mullvad also sells scratch-off voucher cards on Amazon. Amazon would know you are using mullvad but the voucher number is unknown, so the payment/Amazon account can’t be connected to the mullvad account. They only offer 6 and 12 months vouchers, though.

I can access old.reddit.com with VPN. The new shitty layout will block you but there are browser extensions to automatically redirect. I’m never logged in since I deleted my accounts a few months ago.