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Try using below CSS:

<style>
    div[class^="logoCell-"] {
       display: none !important;
    }
</style>

Also, if it is not working using alternate CSS then you can try adding it using SPFx Application customizer (if you want to hide it from all modern pages) or Modern Script Editor webpart (if you want to hide it from only one page).

Reference:

Inject Custom CSS on SharePoint Modern Pages using SPFx Extensions