When is the symplectic group over a commutative ring generated by its root subgroups and a maximal torus? This is related to Symplectic group over $\mathbb{Z}/p\mathbb{Z}$ is generated by its root subgroups. There I was told that in general, the symplectic group $\text{Sp}_{2n}(R)$ is not generated by its root subgroups and a maximal torus.
My question now is: for which commutative rings $R$ is $\text{Sp}_{2n}(R)$ generated by its root subgroups and a maximal torus?
 A: Since $\operatorname{Sp}_{2\ell}$ is simply-connected, there is no need for the maximal torus. So the question is about the triviality of $\operatorname{K_1}(\mathsf{C}_\ell, R) = \operatorname{Sp}(2\ell,R)/\operatorname{Ep}(2\ell,R)$, where $\operatorname{Ep}(2\ell,R)$ is the elementrary symplectic group, that is, the subgroup of $\operatorname{Sp}(2\ell,R)$ generated by its root subgroups.
A lot of cases where $\operatorname{K_1}(\mathsf{C}_\ell,R)$ is trivial are not specific fot the symplectic case and hold for all Chevalley groups. Below is a(n incomplete) list. I only consider commutative rings.

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*$R$ is a ring of stable rank 1 (this includes local and semi-local rings, boolean rings, the ring of algebraic integers, the ring of entire functions, the disc algebra). The proof is a combination of surjective stabiliy for $\operatorname{K}_1$ (a paper by M. Stein) and an easy argument for $\operatorname{SL}(2,R)$ (every its element is a product of 4 elementary matrices, this was apparently first noted by H. Bass);

*$R$ is a Dedekind ring of arithmetic type in a number field which is not totally imaginary (this is Theorem 3.6 from Bass—Milnor—Serre);

*$R$ is Euclidean (the same as the stable rank 1 case, but with the Euclidean algorithm for $\operatorname{SL}(2,R)$ and no bound on the number of elementary factors);

*More generally, if $R$ is a ring such that $\operatorname{K}_1({}\cdot{},R)=1$, it is sometimes possible to show that $\operatorname{K}_1({}\cdot{},R[x_1,\ldots,x_n])=1$, see my answer here;

*There are many papers dealing with the rings of geometric or analytical origin, for example, in this paper by B. Ivarsson, F. Kutzschebauch and E. Løw the authors consider commutative Banach algebras and some rings of continuous functions (they prove that null-homotopic matrices are elementary, but the paper also contains some references for other rings).

