For a functionnal language, TCO is really a must have. How would you do the equivalent of loops without it ?

For a purely functional language. Scheme is not that.

https://www.gnu.org/software/guile/manual/html_node/while-do...

And you are wrong because you can define a loop as iterating recursively over a list with just car and cdr.

Can but since other constructs exist that doesn't by itself make TCO "must have"

I wasn't asking which scheme has TCO.

I was asking which scheme if the 20-50 of them was "lightweight" and embeddable.