Hi,
Very late to the party, almost necro-posting, but there is already a viable solution for a full earth on the fly loading terrain, fully editable in UE5 interface.
Don’t know how they work, if they sell this UE add-on to one person crew or not to, what’s their business plan is, but you could always contact them.
There is already one “game” in the pipeline that is using it, it’s called https://airland.world/. But within this game you won’t be be able to edit the terrain in UE gui but only via Lua scripts in C++, what i think will limit the possibilites.
Wildrealm use the same principle as Outerra, terrain load on the fly (that you can save on the disk so it won’t load online anymore when you’re in the same area) and all vegetation/texturing is procedurally created. Wildrealm also seems to use OpenStreetMaps to create streets/paths/ways/water bodies/agri-fields/buildings, what means ,if you want to change details, you need to modify OSM data for the area you want to represent (what again, means creating an osm private tile server, learning the mapping tools (JoSM in most cases) and spending a lot of time doing it, i tried myself to represent a very small area of northern France in it’s 1940 version, it’s very time consuming).
Creating a flight sim is not a one man crew job.
You can check their Youtube page, even if it’s not updated, to see the possibilites. especially this vid as it shows some interaction with the height and osm data.
Hope i helped a little bit
PS: The hight data 30m for the whole earth, is taking 22.7Gig on the drive, based on Eric Brunetton’s “Proland”, that sadly doesn’t work anymore on win10.
http://proland.inrialpes.fr/index.html