I used Garage 1217 6922 and 6sn7 adapters with great results in a couple MHDT dac’s.
The 6sn7 and 6922 tube replaced the 5670 tube and sounded very nice in comparison. I had a large stash of very nice 6922 and 6sn7’s and was told by manufacture it was okay to run them so why not, but they were only tube buffers.
Not sure I would feel comfortable in a preamp unless amp manufacture could guarantee with no issue, even then would be a little skeptical.
I found the Garage 1217 adapters to be very high quality ceramic sockets and gold plated pins.