Luminescence thermometry has become a popular remote temperature sensing technique for tasks in which traditional contact methods have failed due to their inherent limitations. Here, Er3+/Yb3+-doped Ln2O3 samples have been successfully demonstrated as primary and secondary thermometers in both the down- and upconversion regimes. Boltzmann-type thermal sensing was performed within the range of 298–383 K by monitoring emission transitions originating from 2H11/2 and 4S3/2 levels of Er3+ ion. A comparison of the proposed thermometers was carried out in terms of thermal sensitivity and temperature precision. The crystalline host only slightly affects the thermometric performance – Sr ∼ 1.3 % K-1 and δT ' 1 K for all samples. The practical applicability has been tested on in situ temperature measurement of the graphics processing unit. In general, both primary and secondary approaches provide reliable temperature sensing, which can further enable precise temperature control and monitoring in various fields via luminescence thermometry.