Deprecated function: Creation of dynamic property externalhost line 60 of src/Filebrowser.php

hmm... I can't replicate this.
I used an old site that was created under D6 and upgraded all to way to 11.4

Maybe I am missing something obvious, but I don't understand why the property would be created dynamically.

Steps to reproduce:

Install Drupal 8, filebrowser, configure it

Upgrade to Drupal 9 with filebrowser, use it, add some records

Upgrade to Drupal 10.1 with filebrowser cofiguration, use it, add some records

Upgrade to Drupal 10.4 with filebrowser

Upgrade to Drupal 11

Drupal 11 requires PHP 8.3, which has the deprecated dynamic properties, some record carried over from previous Drupals results in needing this patch.

we're still using this.

Even tough I can not reproduce this error I am seeing some issues with the code that needs te be addressed.
I will come back shortly on this.

I guess you have one or more nodes that have the external host property named as externalhost instead of externalHost.
I have quite a few sites upgraded all the way up from D6.
I also installed a clean D8 site and upgraded all the way to D10 without this issue showing up.

is there a chance you can identify the offending node and get the "properties" value on the table filebrowser_nodes?
Like:

O:30:"Drupal\filebrowser\Filebrowser":28:{s:3:"nid";s:4:"1368";s:10:"folderPath";s:13:"s3://promotie";s:10:"fileSystem";N;s:14:"exploreSubdirs";i:1;s:15:"downloadArchive";i:1;s:13:"createFolders";i:1;s:15:"downloadManager";s:7:"private";s:13:"forceDownload";i:0;s:14:"forbiddenFiles";s:36:"descript.ion
file.bbs
*.git
*.svn";s:9:"whitelist";s:0:"";s:7:"enabled";i:1;s:14:"allowOverwrite";i:1;s:8:"accepted";s:41:"jpg jpeg png gif svg txt doc docx pdf mp3";s:19:"overwriteBreadcrumb";i:1;s:11:"defaultView";s:9:"list-view";s:8:"encoding";s:5:"UTF-8";s:13:"hideExtension";i:0;s:14:"visibleColumns";a:7:{s:4:"icon";s:4:"icon";s:7:"created";s:7:"created";s:4:"size";s:4:"size";s:4:"name";s:4:"name";s:8:"mimetype";i:0;s:11:"description";i:0;s:8:"modified";i:0;}s:11:"defaultSort";s:4:"name";s:16:"defaultSortOrder";s:3:"asc";s:13:"gridAlignment";s:10:"horizontal";s:11:"gridColumns";s:1:"4";s:14:"gridImageStyle";s:9:"thumbnail";s:13:"gridAutoWidth";i:0;s:10:"gridHeight";s:3:"100";s:9:"gridWidth";s:3:"100";s:13:"gridHideTitle";i:0;s:12:"externalHost";s:0:"";}

The properties you see here is from a node that existed already on a D8 version. It correctly shows externalHost.

I could imagine that maybe during the development of the new feature external host, the property name became misspelled, but should flow trough to production.
We can solve it the way you suggest but maybe there is a cleaner solution
Waiting if you can provide further info,
Thanks