Web Access should support using it over multiple monitors, for users where one monitor is too cramped. For inspiration see what VMware does in their web client: https://blogs.vmware.com/euc/2017/04/html-access-horizon-7-1.html This might require single monitor full-screen support first though (bug 5454).
Nice DCV also has some support, but it isn't clear exactly how it works: https://github.com/awsdocs/nice-dcv-user-guide/blob/master/doc_source/using-multiple-screens.md
