If you have a multi-page Gamma site, and want to link to a specific card on a destination page from a source page, follow these steps:
On the destination page, create a button anywhere
Add a link to that button that points to the desired destination card using auto-complete based on the card's header text. e.g., if the card is titled "page 2" have your button link to the card named "page 2"
Publish your site
Load the destination page in a browser
Observe the link on the button you created in steps 1-2, and copy that full URL of the link (including the # parameter of the card to jump to)
Use that full link URL for your link on your source page link. That should lead someone to your destination page and jump to the specific card!