I want to thank Walter McGinnis who gave the answer to this one in another thread:
https://openacs.org/forums/message-view?message_id=18532
I just have to set the hostname to the ip-address as below:
set hostname 192.168.1.10
set address 192.168.1.10
Now I can reach my web server internally from any machine on my LAN😊
Thank you very much Walter!