Linux

There are two ways to do it with KeePass (or KeePassXC or KeePassDX):

1. using the auto-type feature with a virtual keyboard
2. Using it as the desktop's "secrets provider".

When I asked if KeePassXC could work on Wayland, I meant, "does the auto-type feature work yet?" I actually have not looked into using KeePassXC as a secrets provider.

The built-in AutoType feature uses a virtual keyboard to type passwords by switching to the target window and then typing them in as if it were you using a real keyboard. This works in Windows, Android, and X11 (insecurely), but not in Wayland.

On a desktop PC, you can configure the auto-type sequence in an individual entry or on the folder it's in. Then you press Ctrl-V with an entry selected, and KeePassXC will switch to the previous window and start typing like a keyboard. You control when it presses Tab to switch fields, when it types the username or password, and if it hits Enter to submit the login. Stuff like that.

On Windows, the above is secure unless some random app comes to the front as soon as you press the AutoType hotkey. Other programs can't read the keystrokes. On X11 this is insecure. Every program running on the computer can hear every keystroke from every keyboard (real or virtual). This is just one of the reasons why Wayland exists, to eliminate security holes like this, and why KeePassXC under Wayland can't do auto-typing. (Yet)

On Android, you use the KeePass virtual keyboard to AutoType entries. I personally use KeePassDX, but I'm sure there are other ones. Like all Android keyboards, it needs to be enabled in settings before you can use it. You either open KeePass, choose an entry, and then switch to the KeePass keyboard, or switch to the keyboard first, click one of the buttons, and KeePassDX will launch, and have you choose a key to load.

Either way, the KeePass virtual keyboard presents you with buttons for username, password, or any other text fields, and you simply focus the field you want to be typed into, and press the appropriate button. It's secure. Other apps can't intercept the keystrokes. I would screen shot what the keyboard looks like, but I can't do that because of the security settings. KeePassDX blocks screenshots by default, and that carries over to its virtual keyboard.

The other option on Linux is you can configure KeePassXC to be the "secrets provider". Then, when an application does the formal request for a stored secret on the system, KeePassXC provides it instead of KWallet or whatever your DE uses. I have never tried this out, and I don't know how secure it is.