I applaud your initiative, but you should spend some time researching wheel building with an electric motor. The tubeless aspect is another issue entirely — the Montherly and Ambrosio rims you are looking at are tubular, and that type of tire is a closed tube that gets glued to the rim, different from clincher tires that use a tube. Those rims are not at all compatible with Gravelking clincher tires. There is a lot to learn, but wheel building can be very rewarding; it’s simple enough to do it on your own, but complex enough that you can get into trouble if you try to tackle too much too quickly.

I would even say (others may disagree) that a disc brake wheel with electric motor is too advanced for a novice. I wouldn’t try to tackle that, and I’ve built a handful of halfway decent wheels (for rim brakes and no electric motors).