I built a custom Docker image from the official Nextcloud image, which works with the Raspberry Pi 4 and 5. The Docker stack includes a container for Nextcloud, MySQL database, and a Redis Cache Server. I have also added the fixes for adding more PHP memory and adding additional PHP extensions. Video Thumbnails are also supported.
Feel Free to take a look and test it out for yourself. If it all works well for you, please let me know, as I am trying to make sure my custom image is quick and easy for anyone else to use. Also, feel free to explore other containers in my git repo that are fully functional on the Raspberry Pi, such as WordPress, File browser, Nginx Reverse Proxy, and others.