This paper investigates the spectral efficiency (SE) performance of the uplink rate splitting multiple access (RSMA)-enabled massive multiple-input multiple-output (mMIMO) system operating Rician fading channels. To reduce energy consumption, we employ a mixed analog-to-digital converters (ADCs) scheme. Specifically, considering imperfect channel state information (CSI), we deduce expressions for the uplink SE of the user through maximum ratio combining (MRC) detection. Our analysis focuses on the scenario where the Rician factor approaches infinity, offering deeper insights. The numerical findings support the validity of the theoretical analysis and highlight the impact of key factors, including the transmit power, the number of antennas, and the Rician factor, on the performance of the RSMA-enabled mMIMO system.