Summary: We investigate the notion of $S$-flat preenvelopes of modules. In particular, we give an example that a ring $R$ being coherent does not imply that every $R$-module has an $S$-flat preenvelope, giving a negative answer to the question proposed by D. Bennis and A. Bouziri (2025). Besides, we also show that a ring $R_S$ being coherent also does not imply that $R$ is an $S$-coherent ring in general.
[10] Enochs, E. E., Jenda, O. M. G.: Relative Homological Algebra. I. de Gruyter Expositions in Mathematics 30. Walter de Gruyter, Berlin (2011). DOI 10.1515/9783110215212 | MR 2857612 | Zbl 1238.13001
[11] Fuchs, L., Salce, L.: Modules over non-Noetherian Domains. Mathematical Surveys and Monographs 84. AMS, Providence (2001). DOI 10.1090/surv/084 | MR 1794715 | Zbl 0973.13001