I am using libreoffice 6.4.2.2. on Windows 10. I am simply using a right click copy and paste functions from one spreadsheet to another. However when I try to paste I am receiving a text import screen which has changed the formatting. This has never happened before. The only difference is I have changed from TeamViewer to Ultraviewer as my remote system. How do return to a simple copy and paste.
You “copy and paste” what and how? Open your file manager, selects an XLSX (or is that truly “xlxs”?) file there, press Ctrl+C, and then go to an open Calc file and press Ctrl+V? Or use Ctrl+V in Start Center, without open files? or open the XLSX in (some?) application, select a cell range, Ctrl+C, then Ctrl+V in Calc? or even copy a hyperlink to an XLSX in your web browser? Or…? possibilities are ~infinite, and so you didn’t describe your problem at all, even not taking into account that you didn’t mention your OS, and versions of all used applications (LibreOffice at least).
I assume the change in remoting software to be the most important, since those types of softwares like to interfere with content of clipboard.
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be aware that calc copies formulas only between identical versions! since some time, other pastes are ‘resulted’,
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try not to become frustrated by the ‘tone’ of Mike Kaganski,
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there are plenty of copy and paste issues with LO and calc - with OS’s and other applications as well, but less - and as plenty of them are unresolved it’s most likely that nobody can solve your problem,
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search around here and in ‘bugs’,
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try analysing by yourself, it’ll take some time, first try to go back to the old setup, check if issue is gone,
5a. if ‘yes’ try any changes step by step and with modifications to get any clue about the problem,
5b. if ‘no’ try to modify the system regarding the ‘changed formatting’ and find a way to live with it,
the variability and complexity of modern systems and software is immense, and it is!!! difficult to narrow down problems like this, besides that it’s frustrating that such a simple functionality is giving that much problems 
try not to become frustrated by the ‘tone’ of Mike Kaganski,
Since when is a poor question the problem of the guy to call things as they are?