I used pen and paper for a decade now. I have a folder and preprinted forms where I note passwords with pens. The folder had like 20 sheets. This worked pretty well and is without doubt the most secure variant -- I always have my folder with me. Note that this only stores the important passwords. I use weak and dumb passwords for non-important services (similar to disposable email boxes).

Anyway I want to change to a paperless variant due to the increasing amount of "important" services.

I have a friend who does the same, but a folder with password is not encrypted. If it's stolen, or you just leave it somewhere by mistake, or if you leave it on a table while you piss, byebye security... A hacker only needs your old yahoo password to hack everything else. Please use at least Keepass, it has a master password, it is encrypted all the time if you want, it can have browser integration, it can upload the encrypted DB to the cloud..

That's true. However, in general I trust my environment so much more than "the whole Internet" which potentially can gain access to my systems. In fact, I don't think encrypting password managers (even in their simplicity such as https://www.passwordstore.org/) prevent typical use cases: If your home account is compromised, it is easy manipulate the workflow and subsequently decrypt your virtual password storage.