The Temple Institute has been around since 1987. They do good research and education. Great website:
https://www.templeinstitute.org/main.htm
Are they key to rebuilding the Temple? Not so much.
“Are they key to rebuilding the Temple? Not so much.”
Maybe they’ll keep trying, until someone survives the effort. On their mock-up of the Ark, by the way, they didn’t make the cherubim correctly (darker world, this is). They look too romantic and beastly, as if they had little minds of their own.
https://www.templeinstitute.org/vessels_gallery_14.htm
Besides, no one’s going to think about the Ark (Yirmiyahu 3:16).