I built Slicer 4.13.0 in Ubuntu 20.04.3 LTS and then I installed the following extensions using the Extensions Manager:
After the installation, I restarted Slicer but I noticed that only some IGT modules are present, as you can see from the following screenshot:
Searching for OpenIGTLinkIF module I saw this message:
Do you know what I should do to use OpenIGTLinkIF?
If you have built Slicer, then you will need to build all of the extensions that you need as well. The extensions downloaded from the Extension Manager won’t be compatible.
Some more info here: