Best suppressor you have shot on a 30 cal?

You might get a better idea by asking what cans to stay away from since everyone loves their cans.
Most cans work well enough. Some work better than others. It is a lot like rifle and cartridge selection... there are trade-offs in budget, size, weight, etc. This is why you need several ;).

Since the original question was "what is the quietest?" and OP does not care about weight, I assume that suppressors made to be more compact and lightweight are out of the running. This would exclude options like the Ultra 7, Hyperion K, etc. These are good for hunting, but not "the quietest".

Relatively speaking, larger suppressors are quieter. I suspect that there is a yet to be determined limit in size that would serve what he is looking for, but if we were looking at TBAC for example, the Magnus family is going to be quieter than the Ultra 5/7/9 because they are larger (and heavier). The 338 Ultra is the largest they offer, and quietest.

There will be similar options with similar trade-offs from most manufacturers.

A happy medium in size vs sound suppression would be something like the Hyperion. It is 9 inches long and on the upper end of the suppression charts for its size class.

The Pew Science testing is a great resource for comparing options.

Here is some testing that Thunder Beast on a bunch of different suppressors in 2023.

They also did a bunch of testing on their new Magnus line and have the decibel numbers for that as well.

Additionally Pew Science is a good reference as well.

I personally have a Dead Air Nomad Ti, Nomad L and a SilencerCo Hybrid. The Hybrid and Nomad Ti have similar performance despite the Nomad Ti being shorter and half the weight. However they both fall well short of the Nomad L in terms of performance.

You can shoot the Nomad L on a .300 Win Mag with no ear pro for several rounds with no issues while the other two have a lot more crack to them and can cause discomfort over multiple shots without hearing protection.
If I were starting over and looking at a .30 cal can, my first choice would be a TBAC Magnus.

Pretty close volume to my 338 Ultra (which is an awesome suppressor).
My 300 WSM wears a Dead Air Primal, 30 cal end cap with the E-Brake and direct thread. I highly recommend it. It’s awesome. I now wear zero hearing protection when it’s just me and my rifle/Primal setup. Originally, I thought I really wanted a Thunder Beast but I just couldn’t find enough reasons for the significant cash spread at the time. If I had to do it all over again, well I’d do the Primal hands down! Can’t go wrong either way!
The tbac 338 ultra gets my quietest vote. It is big but light. Takes a 16” barrel past 26” when installed. But it makes a 308 as quiet as Ive ever heard a 308 (supersonic hunting rounds). I have bigger cans but they arent quieter, I expect because of both baffle design and bore diameter.
I have an Omega 300 and it is impressively quiet with my 300 BO and 762/39. That is the only one I have shot. Just wish I could get my AR to cycle subsonics with the 762/39. I like the mounting options and I also like the included flash guard that help when I am using night vision.