Hello there
Admitted, I moved from a rather old 2022.6.6 with card-modder to a brand new 2024.1.2, and had the usual amount of fun getting everything working again, but I had to upgrade, as the fix for the August integration did not apply to such old core version.
The issue left now, is with card-mod 3. It seems that no matter what I write in the Style section it doesn’t change a thing on my cards. I would think I have the spelling and indent sright, but because it’s the same problem with all types of cards, surely I must be doing something wrong… 
I am thankful for any help.
Example:
- type: 'custom:simple-thermostat'
entity: climate.stue_aircon
name: AirCon Stue
step_size: 1
control:
hvac:
some_mode: false
another_mode: false
'off':
name: Power
icon: mdi:power
card-mod:
style: |
ha-card {
margin: 0.1rem 0.1rem;
-webkit-box-shadow: 0px 3px 6px 3px rgba(0,0,0,0.8);
-moz-box-shadow: 0px 3px 6px 3px rgba(0,0,0,0.8);
box-shadow: 0px 3px 6px 3px rgba(0,0,0,0.8);
border-radius: 10px;
border: solid 5px rgb(80,120,80);
color: rgb(137, 193, 137)
height: 200px;
--ha-card-background: rgba(20, 20, 20, 0.6);
--st-font-size-xl: 12px;
--st-font-size-m: 10px;
--st-font-size-title: 16px;
--st-font-size-sensors: 8px;
--st-font-size-toggle-label: 8px;
--st-spacing: 1px;
}
Regards Michael J