Deprecation errors with site on subfolder and PHP 8.3

Hello,
Only one site on a given shared host gets the following deprecation errors where all of them are running on same PHP version 8.3 and this one is the only installed on a subfolder:

[21-Apr-2025 09:02:34 UTC] PHP Deprecated:  Return type of HM\BackUpWordPress\CleanUpIterator::accept() should either be compatible with FilterIterator::accept(): bool, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in /.../wp-content/plugins/backupwordpress/classes/class-path.php on line 455
[21-Apr-2025 09:02:34 UTC] PHP Deprecated:  strpos(): Passing null to parameter #1 ($haystack) of type string is deprecated in /.../wp-includes/functions.php on line 7360
[21-Apr-2025 09:02:34 UTC] PHP Deprecated:  str_replace(): Passing null to parameter #3 ($subject) of type array|string is deprecated in /.../wp-includes/functions.php on line 2195
[21-Apr-2025 09:02:35 UTC] PHP Deprecated:  Creation of dynamic property HM\BackUpWordPress\Scheduled_Backup::$backup_filename is deprecated in /.../wp-content/plugins/backupwordpress/classes/class-scheduled-backup.php on line 75
[21-Apr-2025 09:02:35 UTC] PHP Deprecated:  Creation of dynamic property HM\BackUpWordPress\Scheduled_Backup::$database_dump_filename is deprecated in /.../wp-content/plugins/backupwordpress/classes/class-scheduled-backup.php on line 86
[21-Apr-2025 09:02:35 UTC] PHP Deprecated:  Creation of dynamic property HM\BackUpWordPress\Scheduled_Backup::$status is deprecated in /.../wp-content/plugins/backupwordpress/classes/class-scheduled-backup.php on line 92