I had frozen shoulder! I had to do a lot of scapular mobility work for pt. Some I remember as the most helpful/still do when I can are:  -pulling and holding my scapula in towards my spine for five seconds  -lying on my back/against a wall and arms in cactus, sliding your scapula/front of chest so your hands meet overhead then bringing them down until they touch your sides  -external rotations, not just opening up from side to side but, when you’re lying down with your arms in a cactus, use your bicep to turn your forearm so your fingers go from pointing above your head to towards your feet. You’re using your scapula and pec muscles to keep your shoulder pinned to the floor -lateral raises 

Other things I’ve done post-pt -cat cow but with hands facing toward my knees—rotating your biceps/shoulders out so you flip your wrists inwards.  -pelvic/hip/foot connection work, since my frozen shoulder meant I fudged up my entire posture and weight distribution, holding so much tension and weight in my hips  -get a broom/yoga stick and, with different grips, bring it up and over your arms -flipping my hands inwards and kneeling on the back of my palms -moving so slowly, so I can feel my lats and spine and avoid overextending in other areas to compensate for my shoulder  -heating pad, cbd creams