Simbrief does not seem to have a concept of MORA or other kind of safe altitude, neither can I set a minimum altitude in the route database editor. As a result, people are trying to “cross” the Alps in their piston aircraft in unsafely low altitudes, we are talking 6.000-8.000ft. Spoiler, you’ll fly into some cumulus granitus before you make it. LOVV has a “LAL - lowest available level” AIP ENR 6.8 chart that should be used, I assume other FIRs would have something similar.
I do not want to make this into a feature request but I do think a flight planning tool should give you a terrain safe flightplan or at least warn you. I test generated this FP and in 8.000ft as planned you are far below the highest min altitude of 11.500ft or the grid mora of 15.000ft.