Many and varied answers to that.
Are you looking for free software? Are you willing to buy software? If so, what kind of budget?
Lets assume free is what you want.
There is no one software that does it all, you are going to use different software for different things, and sometimes combinations of software to increase the performance. The free or very low cost softwares tend to be focused on ham modes, not general Ute modes. However, they still provide some use in Ute modes.
Demod / decode software:
MultiPSK is a starting point. There is a limited version for free, and a full feature version for a fee. I find the MultiPSK GUI a little confusing, and the learning curve to get the most out of the software is a bit steep.
fldigi is a decent free software. Again, not a wonderful GUI, but a tad easier (in my opinion) to deal with than MultiPSK.
Sigmira is a control GUI for some SDRs, however it also includes demod / decode modules. While meant to take the audio from SDRs, you can also use it with just a soundcard / Wave Mix input.
Sorcerer. This one is a bit of a problem, it is actually commercial, pay, software. However, to the best of my knowledge it is orphaned, the company that made it (Avonlea Services) no longer exists. I think this software was rolled into Krypto500 and Krypto1000 (professional pay software, SIGINT Consulting LLC). So Sorcerer can be found on the web, but be careful, there are both clean and infected versions out there.
Analysis Software (mostly off-line, not real time, for use post recording):
Audacity, or any good audio recording / visualization software. Audacity in particular, and other similar audio programs, can display audio spectrums and spectrographs. These are very useful tools.
Signals Analyzer. This is a low cost pay software, however I am not sure you can still buy / pay for it? The creator died, and I am not sure of the status today. I own a copy I bought years ago. This is a powerful off-line (not real time) tool (for the hobbyist) but the learning curve is very steep. I have heard that there is a free version out there someplace, but do not know that for sure.
Some kind of soundcard oscilloscope software. I use several, but an easy and free(ish) one is Soundcard Scope by Christian Zeitnitz.
Some kind of dedicated audio spectrogram software. Again, there are many, and I use several. But, I really like a very old called Spectrogram16. I think it might have been written for Windows 95 or something like that, but I can still run it under Windows 10 and 11, although the audio routing can be problematic in those OS's.
And, of course, if you already have MATLab there are some decent scripts / programs for analysis out there.
I guess that is a good starting point.
T!