kernel: [549267.368859] mate-terminal: segfault at 2000000101 ip 00007f5d0a9548f0 sp 00007fff7012c610 error 4 in libgobject-2.0.so.0.4800.2[7f5d0a920000+52000]
This seems to be a long-time bug in Mint mate-terminal where you sometimes move or detach a terminal and it crashes losing all of the other open terminal sessions.........
A lot of times these files seem to lag and be incredibly slow even if just a few dozens rows of data.
Here is how you can convert it with "gnumeric":
ssconvert file.xlsx file.csv
You may get lots of weird errors like this but the conversion seems to work fine:
(ssconvert:15244): GLib-GObject-WARNING **: g_object_set_valist: object class 'SheetObjectImage' has no property named 'style'........