No sure about 64gb, but for performance/watt and reliable Linux I can really recommend the Amd p16s and t16(s?) machines from Lenovo. Have about seven in the office and they are excellent.
I too, as someone in devops, am wondering what you need that much memory for. Do you simply really like VMs? :)
Also, have you considered doing the really heavy stuff remotely? Whenever I need desktop type power (16 physical cores and 128gb memory) I simply wake the desktop, ssh into it and do it there.
I’ve been using one full time for about five years now without issue. Even kind of like having to move around a little