Thanks to the previous posters!
Just made this change today on my 2018 Specialized Diverge with a Tiagra 4700 rd. The 11-36t MTB cassette worked perfectly with 48-34 rings! Made a few turns on the B-screw and that's all. Small-small and big-big worked just fine, but I won't be doing those anyway. Previosly had a close ratio 12-28t road cassette back there.
Will take it out for a longer ride looking for some hills tomorrow.