I don’t see a way I can make the buttons larger on the Alarm Panel card.
When it’s used as a wall mounted alarm panel, the buttons are very small, making the text larger, doesn’t make the buttons larger.
The width of the buttons are fine, so they fit in a defined column, but the height is simply too small for a wallmounted display, making it unusable.
I agree, I am using a Fire HD 10 Plus tablet for my alarm system and the buttons on the Alarm Panel Card are way to small. They are hard to read and did not pass the Wife test for usability. I wish you could scale the buttons or set the width/height by a number of pixels and have the buttons scale automatically. I found Alarmo from the Home Assistant Community Store (HACS) allows me to scale the buttons making my alarm panel usable but I would prefer if it could be done locally in Lovelace.
I recommend using Alarmo via HACS. It allows scaling the buttons. It also provides greater functionality and greater ease of use than the built in alarm.