No one has diskspace for perfect, we have to do with “no spikes” and “good mountains”. Now, 20m is best available download for Norway. There is a 10m DEM for Austria.
When I find an issue. I try to solve it. Especially when it does not cost me.. 
this is freeware. Maybe solving the Trondheim spikes is not a priority, because MS/Asobo will replace the whole thing with the next update.
And of course make sure to remove this data from your Community folder prior to the Norway update. I made that mistake once: to leave a London Orbx addon in, surviving the UK MSFS world update. I’ve still nightmares of the view I got. I could sue them for psychological damage. But I won’t, I try to enjoy the game.
With Community, always be carefull. But there is no paranoia needed. Worst case, AP, aircraft and ATC addins can cause a CTD. Bad scenery will look ugly, or give you a low frame rate. When \Community causes issues, you don’t need to remove things. Just park them for a while and wait for an update. Of the addin OR for MSFS. For instance, since october 2020 I have this lovely Ameland airstrip addin, really nice stuff. It worked until december.. then it gave me stutters. But each update, I try to install it again. Just to see if something happened. Don’t be afraid to experiment with Community, it can do no real harm, it is all “sandboxed”.
Here’s the same spot you showed..
