MattiN Yes, you are right. Luckily, the fix is quite simple and I already submitted a pull request for DocLister, see here: https://github.com/AgelxNash/DocLister/pull/378
If you need PHP8 compatibility now, then you can go ahead and just copy the changed yourself via FTP.
I think that Dmi3yy argued this is not Evolution CMS problem but DocLister just to move the issue to the right place. It is true that app like DocLister, MultiTV and SimpleGallery are crucial to a lot of Evolution CMS uses and (as I found out yesterday after my last post) all of them are broken by PHP8. Unfortunately this is a symptom of a way bigger problem, that in my opinion is the biggest problem of Evolution CMS at the time: the add-on store for Evolution CMS is hardly even working. For example if an add-on (snippet, plugin, module) is updated by its dev team, Evolution CMS does not check for these updates. Every site admin has to check themselves. I was dealing with this yesterday, because, ElementsInTree, great Evolution CMS add-on, did not work for me with PHP8, because I was still running some old version of it. Also, if you make a new add-on, then the only way to make it show in Extras is to write an email to Dmi3yy, which is not the best solution.
Unfortunately, this is something that is not easy to fix and the core dev team has to make up their minds on how the add-on store should operate.