deskthority

There are keyboards with Cherry MX Silent Red switches. Those have internal damping making them more silent than other Red switches. The downside is that these keyboards with genuine Cherry MX and especially "Silent" Cherry MX are a bit more expensive. Damped tactile switches exist, but only for those who build their own and that route would be even more costly.

Ducky and Varmilo are brands with good reputation that provide several models with Cherry MX Silent Red. Other brands also have keyboards with them, but I think those are often overpriced for the build quality.

Otherwise you could maybe get a cheap keyboard with anything but clicky switches and install O-rings for sound damping but that will probably not be as silent.
Keyboard enthusiasts have also modified their keyboards in various way to make them more silent: open them up and put sound-damping rubber, foam or bitumen sheets (adds weight for stability and is used for sound-damping in cars) into any cavities that there might be inside the case. If a space bar is noisy, that could sometimes help by lubricating its stabilising parts.
Proper rubber feet and a desk mat underneath the keyboard would also help.

I am in the same boat: first I had a Matias Tactile Pro, then a Model M. But now I am sharing my office with someone, so I had to get something quieter. I opted for the Matias Quiet Pro, which has very nice, tactile but extremely quiet keys. Matias also uses the switch in an ergonomic keyboard and they have 75 % keyboards as well if you don't care for a numpad. The design of some of their keyboards is a bit dated (it is a clone of Apple's keyboards of yore), and I have had problems with keys (which either did not register key strokes or registered them two, three times).

But the key feel is great. Still not as good as nice clicky switches (which is my preference), but for quiet switches they are top notch.