The inability to copy text may be due to an admin setting. At my previous workplace they disabled the ability to paste in images, etc. into Skype for Business saying that it was a security risk. They also disabled the ability to copy and paste between apps except within MS Office for the same reason.
It's not Citrix doing this, but your administrator.
Copy and paste works. They did disabled any communication between the client machine and the Citrix VDI except for audio and camera but the feature I'm complaining about is within the Remote Desktop. It works but its random and terrible. Sometimes you try to copy a single word but it copies the entire message along with the metadata containing sender and timestamp.
It's not Citrix doing this, but your administrator.