1. Introduction  
2. Parameterizing Modified Gravity  
3. Fisher Forecasts  
3.1. Fisher Formalism  
3.2. Spectroscopic Galaxy Clustering  
3.3. Intensity Mapping  
3.4. Angular Probes  
3.5. Fiducial Cosmology, Analysis and Data  
4. Results  
4.1. SKAO Forecasts  
4.2. Combination of SKAO and Next-Generation Optical Probes  
4.3. IM and GCsp Cross-Correlation  
5. Conclusions