I don't really know what went wrong. Perhaps the installation of the tool was faulty but I made 3 USB Ventoy sticks and now all of them are broken.

One of the USBs, a 128GB Kingston stick shows up this error when plugged in to every Windows 10 PC:

"The last USB device you connected to this computer malfunctioned and windows does not recognize it."

I checked online for a whole week doing various fix methods but nothing has saved it so far.

My other two SD cards, a 16GB and a 32GB ones are also broken but they dont show any error message when plugged in at all.

Can I save them or are they broken for good?

Are you using linux? You ok with losing ventoy installation? Use gparted to create new gpt table on the usb drive, and format to something windows likes(maybe fat32, exfat). YMMV, because you give near zero info.

Maybe do the one you haven't tried yet?

Want to know which method that is? Start by telling us which methods you tried!

In addition, the Ventoy version used, the OS it was used on, which filesystem was used for the main data area, any other configuration changes that were made.

I would expect a message of that type if the usb had a non-windows filesystem on it so does it? If it a windows filesystem, that is another problem which might be better resolved at a windows forum. As mentioned above, you haven't posted enough information to get help.