On the 6NS7 tubes, I bought the Don Sach’s Valhalla amp with upgraded Linlai 6NS7 tubes and they sound great. I was able to compare them to the "stock" tubes sent with that amp and they were much better, in my opinion. I haven’t tried the E series of those tubes but I will when these tubes no longer function. There is at least one thread on these tubes. They are larger tubes so you might have to use socket extender(s) to fit them in.
https://forum.audiogon.com/discussions/linlai-e-6sn7-tubes