As far as I know there is no apt package for freeopcua, I guess you installed it by source, can you let me know which version you used? We install the following commit: https:/FreeOpcUa/freeopcua/tree/bd13aee2455c1d137bee45f7d2aedea8dd30115c which works fine for us.

This is an issue with the include directories of freeopcua, see FreeOpcUa/freeopcua#394.

This problem is effectively solved by setting the include directory for BUILD_INTERFACE before freeopcua cmake, but it is better to install spdlog and freeopcua yourself before rcll cmake

Hello,
I have the same issue but could not get it to work with the suggested fixes.

Here is what I did:

1. cloned the freeopcua repo
2. changed the CMakeList.txt for the one from @morxa
3. build it
4. clone the gazebo-rcll repo and build it

the progess stops at 86% and the compitaltion is termiated for the same reason as above.

@hg-tc could you tell me what the steps were which you took to make it work

Best Regards