That’s a 6 year old phone. Not gonna connect to the new watches. There’s great 2nd hand websites (that check everything like IMEI and loan status as well as Apple account locks) that you could easily get a 12 for $230 USD

Damn I thought it was enough to get tapped on the wrist, never wanted the thing to yell at me lol. I’d be just as happy if they ripped the speaker out of the watch, it’s not useful for me, most days

S6 and higher has 3rd gen HR monitor. That’s I think the answer you’re searching for. Unsure which SE has the same sensor