There were some mentions before release about limited multiplayer features like seeing trails created by other players.
Do I need PS+ to see those?
Store page says nothing about it.
No, a PS+ subscription is not required for the multiplayer functions of Death Stranding. The integration of other player's structures, share locker items, etc. should integrate into your world, regardless of PS+ status.
Some sites are reporting that the lack of PS+ requirement is due to the lack of direct co-op play.
Sources: https://kotaku.com/tips-for-playing-death-stranding-1839674810 (Build Stuff section) https://www.tweaktown.com/news/67807/death-strandings-unique-multiplayer-require-ps-plus/index.html (references a limited edition set sold at Game UK starting PS+ not required whose box says "Death Stranding does not require PlayStation Plus". For some reason, this sticker was not displayed on NA limited edition sets.)