The modules maintains bueditor_schema() just for providing upgrade path for Drupal 7 websites, but during installation converts all entries from the bueditor_editors and bueditor_buttons tables to Backdrop style configuration settings and then tries to delete the database table which by that time become unnecessary, but fails to do so.

The reason is incorrect implementation of backdrop_uninstall_schema() function, which expects the module name as function argument:

function backdrop_uninstall_schema($module) {
  $schema = backdrop_get_schema_unprocessed($module);
  _backdrop_schema_initialize($schema, $module, FALSE);

  foreach ($schema as $table) {
    if (db_table_exists($table['name'])) {
      db_drop_table($table['name']);
    }
  }
}

whereas this module is using the database table names instead:

  backdrop_uninstall_schema('bueditor_editors');
  backdrop_uninstall_schema('bueditor_buttons');

Steps to reproduce

1. Install BU editor on site
2. Check that plain text 'text editor' setting is set to None
3. Add a text field (either short or long) to a content type with Text area widget and set Text processing to Plain text rather than Filtered text
4. Create new content with the content type

Expected result : field has plain text area box

Actual result : field has BU editor text area box

There is a comparable D7 issue - https://www.drupal.org/project/bueditor/issues/1931862 and there is a patch. However, the function and variables looks quite different in that function in the Backdrop module so I'm not sure if it can be used directly:

diff --git a/bueditor.inc b/bueditor.inc
index d4af194..66899df 100644
--- a/bueditor.inc
+++ b/bueditor.inc
@@ -81,6 +81,17 @@ function _bueditor_textarea($element, $form_state) {
   }
   $textareas[$element['#id']] = TRUE;
 
+  // Check if this field instance has text processing enabled (filtered text
+  // with text format selection).
+  if (isset($element['#entity_type']) && isset($element['#field_name']) && $element['#bundle']) {
+    $instance = field_info_instance($element['#entity_type'], $element['#field_name'], $element['#bundle']);
+    // If text processing is 0 (plain text), don't show the editor for this
+    // textarea (plain text format doesn't allow any html).
+    if (!empty($instance) && empty($instance['settings']['text_processing'])) {
+      return $element;
+    }
+  }
+
   // Get editors
   if (!isset($editors)) {
     $editors = bueditor_user_eids($GLOBALS['user']);

Tested with default editor after inserting button text: undo removes all text. Redo brings back mangled text. (Used CTRL+Z, CTRL+Y)

With markdown editor button: nothing happens with redo/undo.

This would incorporate buttons array and js library from the markdowneditor module. BUEditor already includes BBCode but markdown is being used a lot more now (github!). It's a small enough addition that it's easier to incorporate rather than just share in some other manner.

With PHP 7.4. the module is giving:

Deprecated function: Function create_function() is deprecated in bueditor_sprite() (line 13 of /home/in/public_html/modules/bueditor/admin/bueditor.sprite.inc).

Implement hook_editor_info() as otherwise BUEditor does not show up in the list of text editors when configuring a filter, for example on /admin/config/content/formats/filtered_html.

I installed bueditor-1.x-2.1 to backdrop-1.2.2 and assign Default Editor to User 1.

But when starring new or editing an existing page, Bueditor buttons were not shown in the Body text area, but they were visible in the Summary text area (If it was activated).

Body text area showed only the buttons of CKEditor but not those of Bueditor. Summary text area showed only buttons of Bueditor, but not those of CKEditor.

I've tried different solutions – I have reinstalled, deleted the cache, I tried all kinds of settings.

Finally I created a new text input text format (named Coder) similar to the Full HTML - without any html restriction or filters. I just wanted to see if the problem would exist it with a new text format

It all started to work fine - both Bueditor and CKEditor become vissible at both Body and Summary text areas. In all text formats including default Filtered HTML and Full HTML.

After deleting newly created Coder text format both Bueditor and CKEditor buttons continue to work fine and now are visible in both Body and Summary text areas in Filtered HTML and Full HTML.

On brush pmu bueditor it's giving:

PDOException: SQLSTATE[42S02]: Base table or view not found: 1051 Unknown table 'db.bueditor_editors': DROP TABLE {bueditor_editors}; Array
(
)
 in bueditor_uninstall() (line 20 of /var/www/html/docroot/modules/contrib/bueditor/bueditor.install).

BUEditor Plus has profiles much like wysiwyg so different editors can be used for different filters. Provides more control over where editors appear.

Might want to also let this take over editor assignment from BUEditor https://www.drupal.org/node/1786686

Every backdrop text format can have a specific editor assigned -- but BUeditor does not seem to be available after enabling the module. Instead, it appears that BUeditor is being attached to every text area, regardless of text format, or any other editors that are already on that format.

BUeditor does not seem to work at all when it's on a format that also has ckeditor on it. If it were available as an "editor" then only one editor would be allowed on the format, preventing this broken state.

The modules js library files, in particular:

 library/bue.min.all.js
 library/bue.min.default.js
 library/bue.preview.js

are referencing backdrop.org instead of backdropcms.org.

Enabling the module on CLI with brush is giving:

The following extensions will be enabled: bueditor
Do you really want to continue? (y/n): y
PHP Deprecated:  Optional parameter $bids declared before required parameter $id is implicitly treated as a required parameter in /var/www/html/docroot/modules/contrib/bueditor/admin/bueditor.admin.inc on line 521

Deprecated: Optional parameter $bids declared before required parameter $id is implicitly treated as a required parameter in /var/www/html/docroot/modules/contrib/bueditor/admin/bueditor.admin.inc on line 521
PHP Deprecated:  Optional parameter $bids declared before required parameter $id is implicitly treated as a required parameter in /var/www/html/docroot/modules/contrib/bueditor/admin/bueditor.admin.inc on line 537

Deprecated: Optional parameter $bids declared before required parameter $id is implicitly treated as a required parameter in /var/www/html/docroot/modules/contrib/bueditor/admin/bueditor.admin.inc on line 537
PHP Deprecated:  Optional parameter $bids declared before required parameter $id is implicitly treated as a required parameter in /var/www/html/docroot/modules/contrib/bueditor/admin/bueditor.admin.inc on line 1021

Deprecated: Optional parameter $bids declared before required parameter $id is implicitly treated as a required parameter in /var/www/html/docroot/modules/contrib/bueditor/admin/bueditor.admin.inc on line 1021

on a system with PHP version:

PHP 8.1.22 (cli) (built: Aug 29 2023 10:48:28) (NTS)
Copyright (c) The PHP Group
Zend Engine v4.1.22, Copyright (c) Zend Technologies
    with Zend OPcache v8.1.22, Copyright (c), by Zend Technologies

The markdown editor icons look a lot better so I've been working on adding them to BUEditor and creating ones to replace the rest.

When upgrading from D7 I see the following notice repeated a handful of times:

Notice: Undefined variable: eid in bueditor_update_1001() (line 58 of backdrop/modules/contrib/bueditor/bueditor.install).

Could create an icon for inserting videos and use this button contribution. Requires video_filter module (which has already been ported to Backdrop).

Bueditor stores editors and buttons in tables and has it's own unique way of exporting and importing them. I wonder how much trouble it would be to convert those to use config?