Bluetooth-Manager 2.4.3: adding a new device is sometimes pair/trust/connect order sensitive

[Groxx]

blueman:

apt show blueman
Package: blueman
Version: 2.4.4+mint2+xia

BlueZ:

apt show bluez
Package: bluez
Version: 5.72-0ubuntu5.5

Distribution: Linux Mint 22.3
Desktop environment: Cinnamon (gnome fork)

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I'm currently running two relatively-stock Linux Mint 22.3 machines, and have been struggling to connect two https://www.socketmobile.com/ UPC scanners. They have a HID mode which has historically worked alright, but we've always had to seemingly-randomly click around the GUI to get it to connect and actually type out any code scanned.

Today I think I've managed to reproduce it, and got it to repeat correctly after a reboot and then on the second computer.

This works, both in Bluetooth-Manager and bluetoothctl:

1. pair (in GUI this shows "connected" notification, but does not connect, and shows "disconnected" after a few seconds)
2. wait for pair to gray out
3. optionally trust (works without) (in bluetoothctl this disconnects the device)
4. connect

This does not (I have not yet tried in bluetoothctl), including after a reboot after trusting:

1. connect
2. optionally trust (pair is not an option) (this DOES NOT disconnect the device)

One of the devices won't reconnect after that failing sequence, it gets into a loop of connect/disconnect/connect that spams notifications (which do not sync up with the events, and continue after closing the UI).

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I very much do not think that these are normal, well-behaving devices... but that "pair, THEN connect" sequence seems functional across many devices. And these work perfectly on every non-Bluetooth-Manager device (multiple of each of android, ios, windows, and mac devices have all used these without any issues), so I'm inclined to think there's something blueman-related going on.

Is that expected and/or a recommended sequence? I really don't know what these separate actions are for, or even where to find out [1], so I'm not sure :\ If it is the right sequence, or perhaps a more reliable one, is there something that should be changed in the GUI's behavior?

1: "help" in the menu provides no help, it's really just an "about", and the closest I can find in the project's github is #2186 . This technically helps, but it's kinda strange to expect random GUI users to search github issues to find out what an always-visible button does. Was this maybe explained as part of a wizard before (#3106)? I don't think I've seen it, so I'm not sure what it did.

[infirit]

The sequence you came to is how bluetooth managers like blueman and bluedevil (plasma) usually add/pair devices. Blueman used to have new device wizard that guides users through this process and make it easier. I like to bring it back so I'll mark this as feature request.

For common devices like keyboards, mice, controllers and audio devices you can usually let BlueZ autopair plugin handle things. In this scenario you just need to connect through the right click menu. Which does not seem to work for certain devices.

And yes, the Help menu doesn't do much, I think it's better to drop it completely.

[Groxx]

I think the info in there is useful (it's far easier to get the version number, for example, than to track down the idk-what-binary, and check its commands/flags/ask apt for idk-what-package's info), just as "about", not "help".

Re pair-then-trust in general: does this actually make a protocol-level difference, or is it more likely something like a bug/race condition in bluez or these devices, and doing it more slowly mitigates it somewhat?