https://manual.limesurvey.org/Optional_settings#Advanced_path_settings

publicurl: This should be set to the URL location of your 'public scripts'. The public scripts are those located in the "limesurvey" folder (or whatever name you gave to the directory that all the other scripts and directories are kept in). This settings is available in config.php and it is used when LimeSurvey need an absolute url (for example when token emails are sent).

Remind : this is not the same than components.request.hostInfo : this one is always used.

Does anyone really use this?

Sometimes it's needed !

Multiple server behind proxy,
Admin GUI disable by host etc …

Then : yes …

Works for me in Version 3.25.14

// debug: Set this to 1 if you are looking for errors. If you still get no errors after enabling this
// then please check your error-logs - either in your hosting provider admin panel or in some /logs directory
// on your webspace.
// LimeSurvey developers: Set this to 2 to additionally display STRICT PHP error messages and get full access to standard templates
    'debug'=>2,
    'debugsql'=>0, // Set this to 1 to enanble sql logging, only active when debug = 2
    // Update default LimeSurvey config here
    'publicurl'=>'https://test.zoo/'

Screenshot 2021-02-19 102700.png (55,755 bytes)   

Screenshot 2021-02-19 102700.png (55,755 bytes)   

Arg : https://discord.com/channels/757925259885412413/757925260476547195/811980157203906570

https://discord.com/channels/757925259885412413/757925260476547195/811974258564792360

OK,

Seems i have a plugin , checked on my 3LTSVanilla : no issue
@mfiora : please : deactivate your plugin one by one

[shnoulle@poledra plugins]$ grep -r --exclude-dir=".git" "publicurl" *
arrayTextAdapt/arrayTextAdapt.php:            Yii::app()->getClientScript()->registerScriptFile(rtrim(Yii::app()->getConfig('publicurl'),"/")."/plugins/arrayTextAdapt/assets/public/arraytextadapt.js");
arrayTextAdapt/arrayTextAdapt.php:            Yii::app()->getClientScript()->registerScriptFile(rtrim(Yii::app()->getConfig('publicurl'),"/")."/plugins/arrayTextAdapt/assets/public/arraytextadapt.css");
arrayTextAdapt/arrayTextAdapt.php:            Yii::app()->clientScript->registerCssFile(rtrim(Yii::app()->getConfig('publicurl'),"/") . '/plugins/cpVille/assets/cpville.css');
arrayTextAdapt/arrayTextAdapt.php:            Yii::app()->clientScript->registerCssFile(rtrim(Yii::app()->getConfig('publicurl'),"/") . '/plugins/cpVille/assets/cpville.css'); // @todo : move it to asset too
HeartBeat/HeartBeat.php:        // Create the endpoint url, Using YII since API have issue with publicurl …
hideEmptyColumn/hideEmptyColumn.php:        //Yii::app()->getClientScript()->registerScriptFile(Yii::app()->getConfig('publicurl')."plugins/hideEmptyColumn/assets/hideemptycolumn.js",CClientScript::POS_END);
hideEmptyColumn/hideEmptyColumn.php:        //Yii::app()->getClientScript()->registerScriptFile(Yii::app()->getConfig('publicurl')."plugins/hideEmptyColumn/assets/hideemptycolumn.css");

Nothing in database too …

Really strange …

Arg … i'm dumb …

        'publicurl' => 'https://demo.example.org',
        'ssl_disable_alert' => true,
        'memory_limit' => 512,
        'max_execution_time' => 120,
        'allowedresourcesuploads' => '7z,aiff,asf,avi,bmp,csv,doc,docx,fla,flv,gif,gz,gzip,ico,jpeg,jpg,mid,mov,mp3,mp4,mpc,mpeg,mpg,ods,odt,pdf,png,ppt,pxd,qt,ram,rar,rm,rmi,rmvb,rtf,sdc,sitd,swf,sxc,sxw,tar,tgz,tif,tiff,txt,vsd,wav,wma,wmv,xls,xlsx,xlsm,xml,zip,css,js',
        'publicurl' => "http://limesurvey.local/3LTS/",
        'deletenonvalues' => false,

No worries, just happens.

See what @mfiora can answer on discord ;)