Is there a way to share the same Keepass database on multiple devices?
I've heard that it can be done with an FTP server, but I am not sure how to set it up or if it even is the best option?
I have an Ubuntu VM that I would like to host the database on (my own physical server).
That means when I make a new username password on my laptop it will automatically do it on my phone as well.
You can share the same Keepass database among multiple devices, but not directly within KeepassXC. The database is just a regular file that will need to be synced between the multiple devices through other means. I am currently syncing between several Linux computers and Android devices. I keep the file in sync by using a Nextcloud (https://www.nextcloud.com) server. You can do the same thing using Dropbox, Google Drive, Microsoft OneDrive, or any other service that lets you keep files synchronized between multiple devices. I have used Dropbox in the past. The Keepass app that I use on Android (Keepass2Android) natively supports several such services.
An open source solution to sync a keepassxc database that does not require a server (contrary to nextcloud that does work really well otherwise) is syncthing, that works via a peer-to-peer synchronization between your devices. The only downside is that if only one of your devices is open at the same time, it will be unable to sync since you need your two devices to be open at the same time so that they can exchange messages… but now phones are typically always open so it should not be much of an issue.
At some points I was also thinking to use the matrix protocol or code something on top of emails to avoid the need of self-hosting a nextcloud instance while avoiding the issues of syncthing, but I never spent time to write it as I have access to a nextcloud instance and I use syncthing otherwise.
For sharing only between Apple devices, by far the easiest method is to put the database files on iCloud and download the Strongbox app for iPhone. That works flawlessly and is easy to set up.
To add non-Apple devices to the sharing group, Mike Cowper's answer is probably the easiest (use Dropbox, OneDrive, or Google Drive instead of iCloud). But I'll mention one quite technical solution that is explained here; it essentially uses three Git repositories: one on iCloud, one on Github (or some other host), and one on your Linux VM. The repository on the iPhone is controlled by an excellent app called Working Copy, which costs $25. You have to push and pull changes for them to sync, and some people won't like taking the extra trouble.
The article is about syncing Obsidian files (a note-taking program), but everything is exactly the same for any type of files, and the method lets you keep your database on iCloud so you don't lose the smooth, trouble-free sharing across your Apple devices. To add another non-Apple machine, you would just set up a git repo on it and link to the Github repo.
