Assigning static IP via GUI

Help and Support Raspberry Pi
4

I just tried that mod (running as root), and got

Traceback (most recent call last): File "/usr/bin/preseed", line 222, in <module> main() File "/usr/bin/preseed", line 121, in main ipv4_configuration["Netmask"] = make_variant(network["mask"]) KeyError: 'mask'
with preseed.cfg as

d-i target/storage string sd
d-i network/interface string eth
d-i network/auto boolean false
d-i network/ip string 10.0.0.163
d-i network/mask 255.0.0.0
d-i network/dns1 string 10.0.0.138
d-i network/dns2 string 8.8.4.4
d-i network/gw string 10.0.0.138

What is the problem, please?