DAVx5 basically acts as the connector between your server and your calendar/contacts/files apps
Thank you for the explanation. I'll probably be testing a lot of FOSS apps on my current android before I make the switch, so it's good to know that I have to look out not just for usability, but also connectivity!
Thank you for the tipps!
A quick google search even reveals a nextcloud tutorial on how to install it . I'll definitely try that out.