I Am Unable to Open This Score

The only result I get is Fatal error: line 2 column 26 No definition for element museScore available.
Search the backup file, see https://musescore.org/en/handbook/3/file-formats#msczcomma
Maybe someone else here can try to fix it.

First I can confirm the crash...
That score stems from MuseScore 3.1 and uses a whole bunch of non-default soundfonts, MDL amongst them. Also the score contains a rather large image. (Nothing fundamentally wrong with any of that, just collecting some facts).
I don't see the message Shoichi sees, but in a current development and debug build I get a stack trace:

1 Ms::Drumset::noteHeads drumset.h 74 0xe24c6b
2 Ms::Note::noteHead note.cpp 811 0x8e26aa
3 Ms::Note::stemUpSE note.cpp 945 0x8e2beb
4 Ms::Stem::layout stem.cpp 110 0x95ce1e
5 Ms::Stem::setLen stem.cpp 131 0x95d001
6 Ms::Chord::layoutStem1 chord.cpp 1490 0x819b02
7 Ms::Score::getNextMeasure layout.cpp 2675 0x8b29be
8 Ms::Score::collectLinearSystem layoutlinear.cpp 114 0xa6364c
9 Ms::Score::layoutLinear layoutlinear.cpp 192 0xa63bd2
10 Ms::Score::doLayoutRange layout.cpp 4410 0x8bc56a
11 Ms::Score::update cmd.cpp 221 0x9c38df
12 Ms::readScore file.cpp 2356 0x65f18e
13 Ms::MuseScore::readScore file.cpp 349 0x64d66e
14 Ms::MuseScore::openScore file.cpp 327 0x64d534
15 Ms::MuseScore::loadFiles file.cpp 304 0x64d1e2
16 Ms::MuseScore::cmd musescore.cpp 6102 0x50a218
17 Ms::MuseScore::cmd musescore.cpp 5910 0x5093dd
18 Ms::MuseScore::qt_static_metacall moc_musescore.cpp 861 0x40c6d0
19 ZN11QMetaObject8activateEP7QObjectiiPPv 0x68c82545
20 ZN12QActionGroup7hoveredEP7QAction 0x27c34ee5
...

Some debug output before that:
Debug: linkPath (...\libmscore\image.cpp:269, virtual void Ms::Image::read(Ms::XmlReader&))
Debug: storePath (C...\libmscore\image.cpp:270, virtual void Ms::Image::read(Ms::XmlReader&))
Debug: Reconnecting broken connectors (3 nodes) (...\libmscore\xmlreader.cpp:632, void Ms::XmlReader::reconnectBrokenConnectors())
Debug: reconnected 1 broken connectors (...\libmscore\xmlreader.cpp:664, void Ms::XmlReader::reconnectBrokenConnectors())
Debug: XmlReader::~XmlReader: there are unpaired connectors left (...\libmscore\xmlreader.cpp:35, Ms::XmlReader::~XmlReader())
Warning: no drumset (...\libmscore\chord.cpp:1754, void Ms::Chord::cmdUpdateNotes(Ms::AccidentalState*))

Seems that last warning is more than just that, as at the same time the stack trace indicated this for class Drumset to be a null pointer?
Is this because I don't have MDL installed?

See #305293: Crash on load if percussion staff with no drumset uses custom notehead