Steps to reproduce the issue

1. Install Joomla! 4 Beta 6

2. Install Phoca Top Menu Module or another extension ( https://github.com/PhocaCz/PhocaTopMenuModule/releases/download/4.0.3/mod_phocatopmenu_v4.0.3.zip )

3. Enable debug mode (to work with not minified JS file)

4. Go to System - Update - Joomla! (Joomla! Update)

Page not responding with following error in console:

default.js?78b00d0ca57c1fd6d2f9ee3935963d7b:217 Uncaught TypeError: node.data is not a function at Object.PreUpdateChecker.checkCompatibility (default.js?78b00d0ca57c1fd6d2f9ee3935963d7b:217) at default.js?78b00d0ca57c1fd6d2f9ee3935963d7b:192 at Array.forEach (<anonymous>) at HTMLDocument.PreUpdateChecker.run (default.js?78b00d0ca57c1fd6d2f9ee3935963d7b:189) PreUpdateChecker.checkCompatibility @ default.js?78b00d0ca57c1fd6d2f9ee3935963d7b:217 (anonymous) @ default.js?78b00d0ca57c1fd6d2f9ee3935963d7b:192 PreUpdateChecker.run @ default.js?78b00d0ca57c1fd6d2f9ee3935963d7b:189

This can be solved when editing the line 217
(media/com_joomlaupdate/js/default.js)

FROM:
+ 'extension-version=' + node.data('extension-current-version')
TO:
+ 'extension-version=' + node.getAttribute('data-extension-current-version')

But then another error occurs:

default.js?2ef16fb02f7b20a2a5704e5f6e9cdd03:306 Uncaught TypeError: Cannot read property 'data' of undefined at PreUpdateChecker.setResultView (default.js?2ef16fb02f7b20a2a5704e5f6e9cdd03:306) at onSuccess (default.js?2ef16fb02f7b20a2a5704e5f6e9cdd03:225) at XMLHttpRequest.xhr.onreadystatechange (core.js?2ef16fb02f7b20a2a5704e5f6e9cdd03:214) PreUpdateChecker.setResultView @ default.js?2ef16fb02f7b20a2a5704e5f6e9cdd03:306 onSuccess @ default.js?2ef16fb02f7b20a2a5704e5f6e9cdd03:225 xhr.onreadystatechange @ core.js?2ef16fb02f7b20a2a5704e5f6e9cdd03:214 XMLHttpRequest.send (async) Joomla.request @ core.js?2ef16fb02f7b20a2a5704e5f6e9cdd03:228 PreUpdateChecker.checkCompatibility @ default.js?2ef16fb02f7b20a2a5704e5f6e9cdd03:213 (anonymous) @ default.js?2ef16fb02f7b20a2a5704e5f6e9cdd03:192 PreUpdateChecker.run @ default.js?2ef16fb02f7b20a2a5704e5f6e9cdd03:189

The source code is:

var extensionId = extensionData.$element.data('extensionId');

Expected result

Information about extensions should be displayed:

Actual result

Information about extensions are not loaded

System information (as much as possible)

Joomla! Beta 6 (4.0.0-beta6)
PHP 7.4.1

Additional comments

Maybe somehow related to: #29980

Jan