The crash report says, that LibreCAD was built for MacOS 11, so it probably can't run on 10.13.6.
I'm not a Mac user and can't estimate or test whats possible with LibreCAD on 10.13.6.
From what I have found, 10.13.6 is end of live, was released 07/2018 and had its last security update in 11/2020.
The situation seems similar to Windows XP. It's support ended long ago, but there are still users who have XP systems running. Meanwhile, the latest LibreCAD builds don't run on XP too.
This is not only a LibreCAD problem. We depend on the development platform, GitHub tools and operating systems. And when Qt or GitHub cancel support for specific outdated operating systems, we can't provide packages any longer, even if we want to.
So you can try to find older LibreCAD packages, which may possibly run on your system.
Or you can try to build LibreCAD from source, if you can.
But, in latest master branch, the minimum requirements have been raised to Qt 5.15 and C++14.
If these requirements are too high for 10.13.6, you may try the 2.2 branch, which should build with Qt 5.5 and C++11.
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
The crash report says, that LibreCAD was built for MacOS 11, so it probably can't run on 10.13.6.
I'm not a Mac user and can't estimate or test whats possible with LibreCAD on 10.13.6.
From what I have found, 10.13.6 is end of live, was released 07/2018 and had its last security update in 11/2020.
The situation seems similar to Windows XP. It's support ended long ago, but there are still users who have XP systems running. Meanwhile, the latest LibreCAD builds don't run on XP too.
This is not only a LibreCAD problem. We depend on the development platform, GitHub tools and operating systems. And when Qt or GitHub cancel support for specific outdated operating systems, we can't provide packages any longer, even if we want to.
So you can try to find older LibreCAD packages, which may possibly run on your system.
Or you can try to build LibreCAD from source, if you can.
But, in latest master branch, the minimum requirements have been raised to Qt 5.15 and C++14.
If these requirements are too high for 10.13.6, you may try the 2.2 branch, which should build with Qt 5.5 and C++11.