Calligra is a office suite and it integrates nicely into KDE and works well on Plasma-Wayland.
sudo pacman -Sy calligra
Install LibreOffice-Fresh in Arch Linux with the following command, replace XX with the according language:
sudo pacman -Sy libreoffice-fresh libreoffice-fresh-XX hundspell-XX
There is as well a older version of LibreOffice, just replace FRESH with STILL to install this one. As LibreOffice constantly improves so many things I would definitely recommend switching to the newer version.
LibreOffice supports Wayland natively, read https://bugs.documentfoundation.org/show_bug.cgi?id=48903. Plasma-Wayland is supporting since version 5.12 as well the XDG Shell v6 and now LibreOffice runs fine (you do not need to set the prefix anymore (GDK_BACKEND=wayland soffice).
LibreOffice 7.0 will replace Cairo with Skia. This will draw the interface with Vulkan. Requires SAL_SKIA=vulkan as a parameter.
With probably LibreOffice 6.1 the KDE integration will much improve, read https://www.phoronix.com/scan.php?page=news_item&px=LibreOffice-KDE5-Backend. This will allow LibreOffice to use KDE’s file and folder dialogs, but sadly loading files via KIO is not supported yet (e.g. if you have a Webdav nextcloud network folder).
OnlyOffice is available as a desktop client but it offers as well a nice integration to Nextcloud. All files stored in Nextcloud can be opened, edited and stored through the integrated Nextcloud client. Only Office offers as well a addon for Nextcloud so that you do not need to install it on a local machine and you can use it directly in your Nexctcloud website online.
Texmaker – LaTEX
As an alternative for the Writer for large documents you can try out Texmaker. It is based on Qt 5 and it is using LaTEX as a back-end, which allows you to create professional printouts without the hurdles of a normal office document writer applications where you can struggle a lot with the formatting.
KMyMoney is a quite good personal finance manager with support for HBCI interfaces to retrieve data from your bank accounts.
In Arch Linux you can install it with:
sudo pacman -Sy kmymoney