Digitally, I use a variation on BuJo rapid logging, implemented in Markdown with plaintext. BuJo itself has become essentially scrapbooking for task management, but the basic idea of logging in bullet lists makes a lot of sense.

Markdown has three legal bullets for UL lists, which along with some sigils after the bullet/space is plenty for complex logging one line at a time. Here's the "key" at the top of each of my journals:

    #### Entry Key
    
    *   Event
    *   Project
    *   Planned Task
    +   New Task
    -   Note
    
    #### Event Status
    
    * ! Key
    * ? Maybe
    * % Cancelled
    
    #### Task/Project Status

    + ! Key
    + ? Watch
    + ^ Tracked
    + ~ Carried 
    + $ Completed
    + @ Delegated
    + % Dropped

Sample log for a day looks like:

    ### Friday :: November 8, 2019
    
    #### Highlights

    -   This cool thing that happened!

    #### Planned

    *   Some event
        -   Meeting notes
        +   Action Item

    *   Some planned task I copied from OmniFocus

    #### Journal
    
    + ^ Follow up on so and so issue
    + ^ Make sure stakeholders aligned
    
    -   Reached out to Coworker
        + $ Wait for followup
        + $ Schedule lunch for Tuesday
      
    - ! Some great idea
    -   DJSON awesome for nested JSON
    -   To extract from logs, wrap with [""]

I use Keyboard Maestro macros to quickly create the header skeletons from templates as needed and I fill in "Planned" during my daily prep. From there it's just appending to the bottom. I also have Alfred workflows and other scripts that know how to append a bullet line to the journal file, which helps a lot for logging notes from anywhere.

Periodically, I search for "+<tab>" in the text file, and it finds all the new tasks I haven't marked with sigils in the gutter row. That lets me quickly move them into OmniFocus for longer-term tracking. Someday I'll script it.

For you, if you really only want notes, even simpler. It's just a day header and appending a bunch of - bullets!

But there'll always be times when it comes down to paper. When all that fails, I have a nice-looking aged-brass Fisher space pen in my front pocket and a Moleskine Cahier (the cheap cardboard ones) in my back pocket. If there's something important to catch unexpectedly the last thing I want to do is fumble with my phone. The notebook is by far the quickest option.

There are some really nice leather wallets for Cahier/Field Guide-sized notebooks, and it actually helps balance my sitting posture by having wallets in both sides. Here's an example of one wallet I bought--I bought both a Horween and Chromexcel version from this seller and they're both high quality.

https://www.amazon.com/Journal-Horween-Leather-Moleskine-ref...

If you make it nice enough to carry around, it quits feeling like a chore to do so.