Starting Gramps via terminal and using the gramplet gives this output:
(gramps:4337): libsoup-ERROR **: 15:13:46.905: libsoup2 symbols detected. Using libsoup2 and libsoup3 in the same process is not supported.
Trace/Breakpoint ausgelöst (Speicherabzug geschrieben)
I read in this thread that you gave up using lmde 6 because of this and other issues.