Have a ultrasonic washer but not knowing what detergent for cleaning soot

I have a (cheap but functional) ultrasonic cleaner.

And I have some items - small connectors having being close to a fire. Those connectors are heavily sooted and I'd like to know what detergent being effective on soot, but also without making any damage to plastic, rubber or metal.

I'm located in Scandinavia, Europe so any product being suggested must also be possible to purchase from Amazon (ebay have some hefty shipping fee for items located in usa, often much more expensive than the product itself).

Try general purpose household cleaner / floor cleaner, in a fairly strong mix with water?

I use that (liquid flash or ajax) for such as watchstraps and jewellery etc., it is very effective.
Rinse thoroughly in clean water and give a couple of extra rinses in the ultrasonic.

For electronics, do the final rinse in the ultrasonic using deionised water & dry with warm air.

I agree in part with "floor cleaner." You have to read the label. Some will be based on ionic detergents, which might leave residues or bound ionic compounds.

I switched to ZEP heavy duty floor stripper for removing flux from whole boards several years ago. It will dissolve acrylic floor wax and even softens cured enamel at higher concentrations. It's main ingredient is butyl Cellosolve (2-butoxy ethanol), which is a great solvent with a distinctive smell and is non-ionic. It's in many such cleaners. Cellosolves are a class of solvents with both a hydroxyl (from ethanol) and ether function (from butoxy). They were invented in the early 20th century, and as a class are great solvents. Most also contain ethanol amine to make them alkaline. That satisfies the need for a saponifier to remove most fluxes.

For removing flux you need about 10% butyl Cellosolve in the final dilution. That's about 1 part of floor stripper to 3 or 4 parts total volume with water. Kesters water-based flux remover, which has the same formulation, starts with a higher concentration of the Cellosolve and is used at about a 1:10 dilution. It needs to be rinsed, and I recommend deionized or distilled water for a rinse.

For removing smoke, you can probably get by with a higher dilution (e.g., 1 part to 10 total). I don't do much restoration and have not tried it. You can probably just follow the label for cleaning, not stripping.

One advantage of ZEP over Kesters is that it's usually available locally and cheap (about $14/gallon in the US). Years ago, I was told it is available in most countries, except Australia. I have not checked since. If you can't get ZEP, its formulation is not unique, and there are probably good substitutes. One thing I would avoid are cleaners with fragrances to give a "clean smell" -- whatever that means.

Thank you guys for most helpful answers.

I found this zepeurope.com web site, so greater chances to get a appropriate product.

[edit]
I filled out the form on the web site mentioned above and asked if ZEP heavy duty floor stripper is possible to purchase from my location (I find the product on Amazon, but doesn't offer shipping).

[edit 2]
I've also asked for this in a local web forum, and got a recommendation for Simple Green all-purpose cleaner. How do you think this product compares to the ZEP heavy duty floor stripper for the purpose of mine?