Welcome to the site.
For those wondering why smokeless muzzleloaders are so hard to find, not even being "offered" now by the big firearms companies,
below is a very good read.
https://apnews.com/adbc910fa9064d4fbdea ... ed-hunters
It's my personal opinion that many if not most these accidents were caused by operator error.
However, one really big "risk" here is that it is relatively very easy to make some of these errors with a muzzleloader compared to a modern cartridge rifle.
Often, these errors would not blow up a traditional black-powder muzzleloader, but they can easily blow up a smokeless muzzleloader because smokeless powders produce so much more pressure. Double load some BH209 (considered a "safe" black-powder, substitute) and you'll likely just have fire come out your barrel; double load some N120 (smokeless powder) and you'll likely have your gun explode in your face.
The above error cannot happen in a modern cartridge gun, i.e. you cannot double-load a 30/06 cartridge into your chamber. But if you were to "double load" a smokeless muzzleloader, that might be comparable to having two cartridges going off simultaneously in a single 30/06 barrel ---- it's going to blow up.
The liabilities and opportunities for life-threatening operator error are simply immensely greater when using smokeless powder in a muzzleloader.
One of these potential risks is accidently loading your smokeless powder in a typical muzzleloader ---- this can be easier to do than many would think, since most muzzleloaders are not designed for smokeless powder, but those using smokeless "pre-package, pre-measure" their loads, which can be easily mixed or confused as to which gun they were prepared.
Merely having smokeless powder in your possession can be a significant risk in that it might get used in the wrong gun.
IMO, this is a big reason the big firearms companies are not offering a smokeless muzzleloader to the general public.