In order for you to play Crusader Kings III on Linux with minimal graphics settings, your computer must meet the following requirements
Operating System:
Ubuntu 20.04 LTS
Processor (CPU):
Intel® Core™ i3-2120 / AMD® FX 6350
Memory (RAM):
4 GB RAM
Graphics Card:
Nvidia® GeForce™ GTX 660 (2GB) / AMD® Radeon™ HD 7870 (2GB) / Intel® Iris Pro™ 580 / Intel® Iris® Plus G7 / AMD® Radeon™ Vega 11
Storage:
8 GB available space
In order to play Crusader Kings III on Linux with maximum graphics settings, you need a computer with a configuration no worse than the following
Operating System:
Ubuntu 20.04 LTS
Processor (CPU):
Intel® Core™ i5-4670K / AMD® Ryzen™ 5 2400G
Memory (RAM):
8 GB RAM
Graphics Card:
Nvidia® GeForce™ GTX 1650 (4GB) / AMD® Radeon™ R9 390X (8GB)
Storage:
8 GB available space