yea the plus lenses are one way, but it would be probably better not to start wearing glasses at all, so then can not harm your eyes in any way, and change your habits for life, or you would need to use plus glasses forever if you continue long smartphone use.
I would first get rid of long close-up activities and of course, if you need to use the phone, better install some screen time protecting app. Let the app protect you from the phone.
Then I would try to do distance active focus for a very long time.
If it would not help at all, I would probably try the plus lenses as a last option to improve. I think they could help to have a strong stimulation, like the opposite of hyperopic defocus, which happens when you wear too strong glasses. So that could be more effective than active focus. But I dont know if it’s true. This is an interesting topic, I don’t know if Jake or someone else has thought about it.