Have you checked that mobile data is enabled for SIM 1 in the SIM card manager.
Settings > Connections > SIM card manager > Mobile data (SIM card 1)
Got the same issue after the update in UK... slot 1 no mobile data... slot 2 works perfect... strange is that if I let data on and move around the city at some point I get internet.. 4g and 5g... as soon as I switch it off it won't go back on again so is definitely a software problem here. Samsung?
Also got the advice written above... put sim in slot 1, activate you data, on settings, mobile networks, network mode... select 3g/2g first and you get H/H+ after select the one above LTE/3g/2g and after the option 5G/LTE/3G/2G AND YOU GET 4G+... Now don't know how much will last or if you need to do this all the time... hope Samsung working ok it because is no reason to send the phone for repair...