Leadwerks was super buggy for me on Arch, it kept crashing...
So I did 2 things to get it working properly and flawlessly.
1. Using the beta branch.
Using the beta branch corrected for me the crashes when a file dialog was supposed to pop-up and some others.
To use the beta branch you need to right click on Leadwerks on steam then click on properties, as shown below.
The properties panel will then show, select the betas row and select beta as shown below.
2. Installing libcurl-compat
Installing libcurl-compat from the community repos solved