I installed Anki Desktop from source (github) on my desktop machine with Linux Mint 20.1 Ulyssa.
Anki Desktop is able to start but several GUI elements are not visible (like the front and back of notes).
This is the output when I launch Anki Desktop from terminal:
Qt debug: using qt5ct plugin
Qt debug: D-Bus global menu: no
JS error /_anki/pages/deck-options.js:50 Uncaught ReferenceError: globalThis is not defined
Not found: 'favicon.ico'
JS error /_anki/pages/deck-options.html:1 Uncaught TypeError: Cannot read property 'deckOptions' of undefined
JS error /_anki/js/reviewer.js:7 Uncaught ReferenceError: globalThis is not defined
JS error :1 Uncaught ReferenceError: _showQuestion is not defined
JS error :1 Uncaught ReferenceError: _drawFlag is not defined
JS error :1 Uncaught ReferenceError: _drawMark is not defined
JS error :1 Uncaught ReferenceError: getTypedAnswer is not defined
JS error :1 Uncaught ReferenceError: _showAnswer is not defined
JS error :1 Uncaught ReferenceError: _showQuestion is not defined
JS error :1 Uncaught ReferenceError: _drawFlag is not defined
JS error :1 Uncaught ReferenceError: _drawMark is not defined
JS error :1 Uncaught ReferenceError: getTypedAnswer is not defined
JS error :1 Uncaught ReferenceError: _showAnswer is not defined
JS error :1 Uncaught ReferenceError: _showQuestion is not defined
JS error :1 Uncaught ReferenceError: _drawFlag is not defined
JS error :1 Uncaught ReferenceError: _drawMark is not defined