I'm trying to get the best surround sound. My stereo receiver is older and has HDMI outputs as well as optical. I'm using optical and it allows Dolby Digital but not DD plus. My receiver only supports DD+ through HDMI connection. There probably isn't a way to output HDMI to stereo without ARC support? I think maybe long term I need a newer receiver with ARC.
TV is Hisense 70A6G3
Receiver is Sony STR-DH800
Don't get too excited about ARC -- it supports exactly the same audio formats as optical.
You have to jump to eARC to get the higher bandwidth options like DD+
Looking up the specs for that TV I don't see eARC, so you're probably getting the best audio output it supports.
Some more details here: https://www.tomsguide.com/us/hdmi-arc-faq,news-26262.html