Just locate your options.txt in android, data, hearthstone and at the end add a line “targetframerate=60” (without “” and type the value you want), add another line with “vsync=0”, done!
Its running super smooth at 60, but the patch destroyed the performance so be aware that it stutters really hard sometimes until they fixed it. Happens on my Note 9 and Tab S6 with Snapdragon 855.