Actually, to precisely determine the band gap value from the Tauc plot, one should normalize obtained Tauc function and then necessarily draw the tangents: one paralell to the X axis and one extrapolated along the function slope to the X axis. Then - your band gap value lies at the tangents intersect. Please look at the article below and also at the attached file with my Tauc plot presenting the correct way of Eg determination in pdf.
Article How To Correctly Determine the Band Gap Energy of Modified S...
plz use modified Tauc equation by Kubelka on you DRS data and then plot graph in Origin 2020. Extrapolate the the graph and its cut at X axis will give you exactly value of Bandgap energy between BB and CB. There may be Urbach energy due to defects in your sample.