I have the same problem. I just got a new phone. Samsung Messages had Chat settings on my Note 5, but there isn't any Chat setting on my Note 10 even though my messages are indeed Chat type messages.
I had this problem , i am in uk and i ported my number from another network to current network , this does not update the sim card mobile number so old number still stays inbedded in the sim so when going into settings and about phone you should see a mobile number it will show the previous number not your number , when i downloaded google messages and enabled chat i had to clear data from the app and input my current number this then enabled chat features RCS however with samsungs messages app all i got was a N and pop up for agree to chat features terms so agreed but it would not connect like googles messages app did the menu in samsung messages app was missing chat menus due to it not enabling , i had problems with three mobile data not coneecting loading slowly so they sent out new sim card i had this activated , now the mobile number is shown in about section of settings as unknown so the samsung messages app i cleared data cache and opened it up i got the terms agreement pop up like before so again agreed then another pop up which i didnt get before to input my mobile number using region +44 code then my number so inputted this and RCS chat features menu appeared and was activated just like googles messages app , i can now see when message is delivered to someone else using rcs and when they read my message and when there typing too , bubbles are green for sms/mms and blue for RCS . You can change default setting to chat or sms/mms or set automatic other settings besides are available to customise too . So it appears that the messaging app requires current mobile number to work as it searches the default number within about section of phone on sim card which you cannot change yourselfs .