apt update時に一部のリポジトリで以下のようなメッセージが出ていました．特に問題はないので放置していましたが直してみました．
$ sudo apt update --snip-- Notice: Skipping acquire of configured file 'main/binary-i386/Packages' as repository 'https://brave-browser-apt-release.s3.brave.com stable InRelease' doesn't support architecture 'i386' Notice: Skipping acquire of configured file 'main/binary-i386/Packages' as repository 'https://download.vscodium.com/debs vscodium InRelease' doesn't support architecture 'i386' --snip--