I believe this article makes it sound more difficult than it really is. I have been testing this for a while now.
- Configure the New Teams optimally in the VDI environment
- In Citrix Studio > Policy make sure that the policy for Virtual Channels is enabled and define the proper virtual channels for new Teams
- On the Windows client endpoint make sure Citrix Workspace is installed with the optional component for the Teams Plugin enabled (it asks you during an install of Workspace)
- Connect as usual. The first time it will negotiate and do is thing and display in the Teams About as being Citrix Optimized. But the next time you start Teams it will then indicate it is Slimcore Optimized
More granular instructions from Citrix are here: https://support.citrix.com/s/article/CTX691425-how-to-enable-teams-optimization-with-microsofts-new-vdi-optimization-engine-slimcore?language=en_US