I bought my turbotax at Costco, where is the activation code since it's download only in 2025?

Yes, VolvoGirl, the process now is as you describe.  Just bought TT Deluxe at Costco yesterday, took the display card and receipt to the service window beyond the checkout counters, and exchanged for a cardboard package that contained the code.

No, only if you bought in the store.  

I'm on Windows 10.  This is how mine went.
1/3/25 Bought Home&Business from Costco online.  20 min later got email with License Code and download link. Clicked on Download link. It took me directly to Turbo Tax to download. Had to pick my product then select Win or Mac. Program downloaded.

Had to go to my Downloads folder. Clicked on downloaded .exe file. It started but stopped saying I needed Microsoft Visual C++ with an install button. I clicked on it and it installed the MS Visual C ++. Then it continued to install Turbo Tax.

Checked on the License Agreement. Clicked on Install. Minute later it was done and launched.

Sign in to Intuit Account, had to get email code to enter.
Got License Code screen. Went and copied 16 digit code from email and pasted it into code box.
Got into program.

First thing I did was check for updates. Then I always go up to Online-Updater Preferences and check Ask me before getting updates.

No.  You need a full Windows or Mac computer to install the Desktop program.   2024 Turbo Tax Desktop Download System Requirements  Windows 10 or later or Mac OS Ventura 13 or later
https://turbotax.intuit.com/personal-taxes/cd-download/tta-system-requirements

So you either need to find another computer to install it or get a refund and use the Online browser version.

Where to find the License Code
https://ttlc.intuit.com/community/tax-topics/help/i-can-t-find-my-license-code/01/852973

How to get started with the Desktop program, install and activate it
https://ttlc.intuit.com/turbotax-support/en-us/help-article/product-delivery/download-software-turbotax-com/L7u9oLEkq_US_en_US?uid=luqgvzrd