Hello Veronica and welcome aboard!

You made the right choice by choosing Elgg for your social app.

Is Elgg still updated and "taken care of"?

Elgg is constantly updated and supported:
https://learn.elgg.org/en/5.x/appendix/support.html

This is how it happens on GitHub https://github.com/Elgg/Elgg/commits/master

I see a lot of posts hundreds, if not thousands, of days old

In fact, Elgg as a framework is stable and reliable, perhaps it lacks a good user interface, but there're also developers who will help you improve your app for free or for a fee.

The decrease in activity occurred due to the fact that more and more Elgg developers “grew up” and Elgg as a free and open source product rests only on enthusiasts.

There's a Telegram channel that regularly published info about all Elgg plugins and releases, as well as other useful information. Subscribe here: https://t.me/elggnews

There's chat also where you can ask questions just like in this Community: https://t.me/elggchat

unfortunately I can't seem to attach a screenshot

This community aka forum is made on the basis of Elgg version 2 and the administrators simply don't have enough time to update this site: https://elgg.org/discussion/view/3290256/elgg-community-future

That's why many things here still look strange ;)
 

is there any way I can upload an Excel-file to a group

By default, activating the "Files" plugin allows users to upload any files, including Elgg.

In the future, they can only be downloaded.

There's a 3rd-party plugin lets users preview MS Office files (doc, docx, xls, xlsx, ppt, pptx), Apple iWork pages, Adobe eps, and zip files.

I've never used it but you can download the version for ElGG 5 here: https://github.com/rohit1290/gdocs_file_previewer

 and then let the group members edit it right there?

There are no plugins for collaborative document editing for ElGG 5.

For this you need to hire a developer ¯\_(ツ)_/¯

https://elgg.org/groups/profile/75603

Hi Nikolai, and thank you for your kind and explanatory answer!

I get a followup-question on this: 

is there any way I can upload an Excel-file to a group

By default, activating the "Files" plugin allows users to upload any files, including Elgg.

In the future, they can only be downloaded.

I installed the Files plugin and managed to upload the excel-file, but if it's not editable from within the "Elgg-community" I'm planning on creating (for a non-profit organization) I will probably work with onedrive, so that will be alright, but what I don't understand above is this: "In the future, they can only be downloaded."

Is the possibility to upload files going to be removed? 

I'm thinking that then there should subsequently be no files to download either...?

Maybe I'm misunderstanding?

Thank you for all the useful links!

//Veronika

The ability to download or upload files is a default feature in Elgg.
But this option can be overridden in your custom plugin.

So :
1 - You must create a custom plugin with collaborative document editing, OneDrive integration features etc
2 - In this plugin, limit file downloads/uploads if you need this option

I've never heard of such a problem in Elgg but there're a few Q&A on StackOverflow. 

Basically, this issue is related to PHP session or php.ini configuration: 1, 2.

Do you have any custom settings in php.ini? 
Are there any other errors in the server error logs? 

You can also look at the Elgg settings if you need something special. 

For example, I recommend using a custom session name but not 'Elgg':

$CONFIG->cookies['session']['name'] = "YourAppName";

Hello, 

thanks for yout reply. No, there Aren't any specials in php.ini. 

We just tried it with composer. But there, we reach our memore-limit:

First try with 512M instead initially 256M:

XXXXXX@ssh:/var/www/XXXXXX/html/ELGG$ php -d memory_limit=512M composer.phar install
No composer.lock file present. Updating dependencies to latest instead of installing from lock file. See https://getcomposer.org/install for more information.
Loading composer repositories with package information
Info from https://repo.packagist.org: #StandWithUkraine
Updating dependencies

Fatal error: Allowed memory size of 536870912 bytes exhausted (tried to allocate 8192 bytes) in phar:///var/www/XXXXXX/html/ELGG/composer.phar/src/Composer/DependencyResolver/RuleSetGenerator.php on line 68

Check https://getcomposer.org/doc/articles/troubleshooting.md#memory-limit-errors for more info on how to handle out of memory errors.

Second try with 768M

XXXXXX@ssh:/var/www/XXXXXX/html/ELGG$ php -d memory_limit=768M composer.phar install
No composer.lock file present. Updating dependencies to latest instead of installing from lock file. See https://getcomposer.org/install for more information.
Loading composer repositories with package information
Updating dependencies

Fatal error: Allowed memory size of 805306368 bytes exhausted (tried to allocate 41943040 bytes) in phar:///var/www/XXXXXX/html/ELGG/composer.phar/vendor/composer/semver/src/CompilingMatcher.php on line 92

Check https://getcomposer.org/doc/articles/troubleshooting.md#memory-limit-errors for more info on how to handle out of memory errors.

Elgg installation via composer:

composer self-update
composer create-project elgg/starter-project:dev-master /var/www/XXXXXX/html/ELGG
cd /var/www/XXXXXX/html/ELGG
composer install

What's OS on your server?

No edit option to edit the above.

I have an site based on Elgg since the beginning of 2010. The site has a few 1000 members. But most of the members are not really active (the site has some specific theme and it's required to join to see anything so quite a number of people joined to look around but never returned or stopped visiting after a while). And it seems people stay more on a few large sites and ignore the many, many other sites available.

I've started with Elgg 1.6 and bought some commercial plugins when I started with the site with the intention to rely on Elgg core and these plugins also on future versions of Elgg.

Well, it didn't work out this way. Elgg got updated regularly ever since then but almost all the 3rd party plugins I'm using got abandoned (regardless if free or bought). So, I've started to learn maintaining the plugins myself to be able to keep the site at least up-to-date somehow.

Maintaining a lot of plugins on your own - in your spare time - is not easy. So, I'm quite behind with keeping the plugins working on more recent Elgg versions. Right now my site is still on Elgg 2.3...

My experience: try to use as few 3rd party plugins as possible. Elgg core gets updated but keeping the 3rd party plugin up-to-date can be hard (both for the developers or for you if you try it on your own).

Choose any 3rd party plugins carefully. Any plugins written by Coldtrick are safe to use because the same guys also maintain Elgg core and get their own plugins updated regularly. Any other plugins might require work on your own or maybe future investments to get them updated.

But any other social network frameworks might not be better either... I have to admit I'm not keeping informed about any others. But they either will cost from the beginning or might cost for customizations (if even possible depending on the license used or if maybe even closed source code). And any predictions about the future of Elgg and other systems is futile. Nobody could say for sure what will be in some years from now. At least Elgg is open source and free. So, there's always the option that someone else can continue.