You could consider a class D amp with a tube input buffer. The Purifi modules add very little of their own sound signature, but require a front-end driver board to provide some gain and impedance matching. There are a couple of companies that make amps using these modules (which are very efficient) that use a triode-based front end.
https://vtvamplifier.com/product/vtv-amplifier-stereo-purifi-audio-1et400a-amplifier-with-vtv-vacuum...
ATM makes an Korg NuTube based input buffer. I assume they make a complete amp that uses this buffer, but I don't know the model. The ATM buffer seems a bit pricey for what it is, but it might sound good.
https://atm-audio.com/product/buffer-korg-nutube-for-hypex-nc500-and-purifi-audio-1et400-v2/
I haven't heard either of these, but have heard an amp using the Purifi module and it is very clean and detailed.
https://vtvamplifier.com/product/vtv-amplifier-stereo-purifi-audio-1et400a-amplifier-with-vtv-vacuum...
ATM makes an Korg NuTube based input buffer. I assume they make a complete amp that uses this buffer, but I don't know the model. The ATM buffer seems a bit pricey for what it is, but it might sound good.
https://atm-audio.com/product/buffer-korg-nutube-for-hypex-nc500-and-purifi-audio-1et400-v2/
I haven't heard either of these, but have heard an amp using the Purifi module and it is very clean and detailed.