Sorry for the nuisance. Extension:CookieWarning doesn't disturb 1.35.1. Function not visible, perhaps because I'm the site admin. Feel free to remove the task completely. However, a note may be added to the extnsion page about the needed wiki version.

Declined

Hello, there is a new version "7zip 21.00".
--amended:--
I tested it with a 1.34.2 download (using BeyondCompare, a great software for folder and file comparison), and the problem is still there. Fortunately, the files with truncated filenames have, been identical to old ones or replacements for old ones which gave me the correct name.

I understand that you are asking because of the error message. Well, yes, for sure, I double-checked it. Although I never type off but extract and copy the downloaded extension installation packages. So if there were an error it would be in the installation package. I fear I can't be of more help.

Folder was 750 for "Rechte" (32678 for Besitzer, 99 for Gruppe). Set to 754.
File was 640 for "Rechte" (32678 for Besitzer, 99 for Gruppe). Set to 644.
Same fatal error :-(
I never before in any extension had to change an attribute.

As the Wiki doesn't start with SelectCategory activated I can't tell whether the bug itself is still there :-(
The installation code in LocalSettings wasn't changed. The issue exists since installation of 1.34.1 in April 2020. Yesterday I tried once more, without result. I even changed the line

require_once( 'extensions/SelectCategory/SelectCategory.php' );

according to the prescription in MediaWiki to read

require_once( '$IP/extensions/SelectCategory/SelectCategory.php' );

without result. I suspect an incompatibility with 1.34.1?
Oh, wait, you said "branches", I read the MediaWiki page once more, and another link seems to offer another version (different file name, at leas)t. I'll try it out and report back soon. - No, still fatal error.
Cheers, Winfried

running 1.34.1 now, I get this error message when activation the extension