From the way you are writing this it seems like you are referring to plone 6 classic not plone 6 (ie plone 6 volto)
We have some patches to plone 6 to put Tus support back into the UI but haven't got it into a PR form yet. We've had to make changes to the rest end point to get over some speed issues.
As far as I know Tus should still work in classic. No extra imports would be needed.. but I haven't tried it. You should just need to set the env bars on where to put the temp files and set things up to ensure that all instances have access to the same temp file.