• a fake analog clock (AliExpress)
• a silly door note like "behold, engineers in their natural habitat"
• a set of hex wrenches
• an empty box, but there's a game gift code on the inside, or an envelope :p
• a pack of sticky notes labelled "floppy storage medium" or "offline, airgapped, ultra reliable, infinite battery.. password manager"
• fancy coffee (for those late night coding sessions)

.. and every time I have to think of a gift, I can't :p

I'e got more ideas but this post is getting long

Some people consolidate on things in their 60s after retirement and don’t necessarily want more things. If this person has shown signs of that - then something disposable like food/snacks/sweets.

I make cookies or canned jams, jellies, candied jalapeños. Edible so they will not clutter forever.

What's their opinion on puzzles and such? There are some fun wooden gizmos with gears and what have you

One gift I've been giving out that's pretty popular is an automatic foam soap dispenser. It's a nice little quality of life improvement and since you add water to the soap to make it foamy, soap lasts a lot longer too.

There are a bunch on Amazon. I would find one that you like the look of and make sure it charges with USB C.

My go-to is the biggest pack of AA or AAA batteries you can fit in your budget. They're always handy.

An idea that I had was I went to an import store and got my sister a small tea set with Japanese writing on it talking about sweet rolls. A small novelty item that I would never find in my hometown. It cost me about $3 so perhaps you can find something unique like that.

Arduino board or similar with a basic start kit?

What is your budget?