HMD is betting that consumers are moving to more environmentally-conscious products and are placing an emphasis on repairability. HMD says the Pulse range is built to “Gen 1 repairability” and that users can pick up self-repair kits from iFixit. Repairs include changing the battery, but also swapping the screen.
Looks like the back (and side) cover clips on. IFixit has repair guides available already. Inside, it looks like basically any regular phone. No Fairphone-esque modules. The inside seems to be well-designed for repairability though -- separate bottom board and battery pull tabs. All of the side buttons are attached to the back cover and a thin cable connects to the main board under some plastic. That's going to be easy to break while repairing...
I looked at all 3 phones, they are all similarly built to the Pro model I linked.