Very interesing. For the US, it looks like the DEM should be available at a 1 meter resolution....
Online here I can see what looks like 10 meter resolution:
https://viewer.nationalmap.gov/basic/?basemap=b1&category=ned,nedsrc&title=3DEP%20ViewIt comes in garmin IMG format, which has DEM inside of it. I dont know how easy that would be to import into trekarta, but it should be significantly higher resolution for some areas
(rather than 100 meter or 50 meter, 10 meter is not bad. The 1 meter data seems very incomplete )