Suggestions for Linux-friendly BLE dongle?

I bought this Bluetooth dongle for a desktop computer running Ubuntu 20.04 LTS, using bluez. It works with my wireless headphones but does not get along with my Bangle.js 2. It regularly takes a dozen attempts or more to connect without giving an error, and even then it might only stay connected anywhere from a few seconds to a minute or two before erroring out and disconnecting, regardless of how close the dongle and watch are to each other. I have a laptop running the same version of Ubuntu, and its built-in Bluetooth works fine with the Bangle. Oddly, I tried this dongle on a Windows 10 system and it seemed to work fine there, too, so maybe the Linux drivers for that chipset are buggy?

To preserve my sanity, I was thinking of trying to buy a different dongle in the hope that I get one that works better. Is there anyone here who successfully works with Bangle BLE on Ubuntu or a similar distro (like Debian or Raspberry Pi OS) who could suggest a specific dongle that seems to work well with it? Or any other suggestions for this problem?

Or any other suggestions for this problem?

Can you show output of dmesg when you plug it in? Does it load any firmware file? I have a bt 5.3 dongle that by default behaves is similar way (mostly does not work) and it was old linux firmware, when I googled it I found people with same problem and solution was to copy firmware from windows driver installation to linux into /lib/firmware. After doing that it works perfectly and since then it is the best bt dongle I have.

mine says

[ 9058.109616] Bluetooth: hci0: RTL: examining hci_ver=0a hci_rev=000b lmp_ver=0a lmp_subver=8761
[ 9058.111717] Bluetooth: hci0: RTL: rom_version status=0 version=1
[ 9058.111736] Bluetooth: hci0: RTL: loading rtl_bt/rtl8761bu_fw.bin
[ 9058.112034] Bluetooth: hci0: RTL: loading rtl_bt/rtl8761bu_config.bin
[ 9058.112217] Bluetooth: hci0: RTL: cfg_sz 6, total sz 28410
[ 9058.382728] Bluetooth: hci0: RTL: fw version 0xdcc6b3a8

and some Amazon reviews from your link say it is based on rtl8761bu, check this https://www.reddit.com/r/linuxhardware/comments/ynjvkx/bluetooth_53_linux_support/

I just copied rtl8761b_mp_chip_bt40_fw_asic_rom_patch_new to /lib/firmware/rtl_bt/rtl8761bu_fw.bin as is.

It'd be great if you could lsusb and post up the USB IDs? It might help others find similar dongles/solutions.

A few years ago I bought a bunch of dongles and made a list at https://www.espruino.com/Quick+Start+BLE#requirements but there are no BLE 5 dongles in that list.

I'm still doing all my main work using a Broadcom BCM20702A0 based BT 4.2 module and it's been pretty reliable for me.

It'd be great if you could lsusb and post up the USB IDs?

the reddit thread has it, I think mine is that 0bda:a729 Realtek Semiconductor Corp. Bluetooth 5.3 Radio mentioned there, will check later EDIT: yes, that's it

I'm still doing all my main work using a Broadcom BCM20702A0 based BT 4.2 module and it's been pretty reliable for me.

the 5.3 one I have is good because it can also do coded phy - long range of 52840, however linux/bluez support for it is not great overall, but at least scanning for extended advertising over coded phy works

but at least scanning for extended advertising over coded phy works

That's very cool. Yes, I've been missing being able to do that.

A few years ago I bought a bunch of dongles and made a list at https://www.espruino.com/Quick+Start+BLE­#requirements but there are no BLE 5 dongles in that list.

the reddit thread has a link to this https://medium.com/codex/bluetooth-5-on-linux-overview-of-kernel-supported-dongles-and-chipsets-c6f2b632b236

This is all I get when I plug in the dongle:

[3709401.040967] usb 2-1.7: new full-speed USB device number 85 using ehci-pci
[3709401.158174] usb 2-1.7: New USB device found, idVendor=7392, idProduct=c611, bcdDevice= 2.00
[3709401.158180] usb 2-1.7: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[3709401.158182] usb 2-1.7: Product: Edimax Bluetooth Adapter
[3709401.158183] usb 2-1.7: Manufacturer: Realtek
[3709401.158185] usb 2-1.7: SerialNumber: 00E04C239987

No mention of any firmware loading here or in any of my system logs, so I have no idea which firmware file to target. :(

That's odd. The usb vid/pid is different from mine but someone here does see the firmware loading messages with your one https://forums.debian.net/viewtopic.php?t=155644

Strange. The forums post shows loading rtl8761bu_fw.bin, but my /lib/firmware/rtl_bt directory does not have that file. The closest filename present is rtl8761b_fw.bin.

I found a Linux driver download on the manufacturer's website (http://www.edimax.com). This ZIP file contains a lib/firmware with a rtl8761bu_fw file (not quite the same naming scheme). Then it has lib/firmware/rtl_bt with a handful of other files in it and a lib/firmware/rtlbt with a rtl8761b_fw. This isn't very consistent with the organization of my system's /lib/firmware directory. I can't really make heads or tails of this.

It probably differs between linux distros, however even with no firmware present on disk you should see lines similar to those

[ 1368.955155] Bluetooth: hci0: RTL: examining hci_ver=0a hci_rev=000b lmp_ver=0a lmp_subver=8761
[ 1368.956133] Bluetooth: hci0: RTL: rom_version status=0 version=1
[ 1368.956136] Bluetooth: hci0: RTL: loading rtl_bt/rtl8761bu_fw.bin
[ 1368.956155] bluetooth hci0: firmware: failed to load rtl_bt/rtl8761bu_fw.bin (-2)

when bluez tries to use the device. You mentioned ubuntu 20.04, that is quite old, I use 22.04 and it is directly in /lib/firmware like in the edimax zip, anyway you can try to put that file to your location.

Yeah, I don't get any of those “Bluetooth:” lines in my system logs at all. I looked in /var/log and in the systemd journal for bluetooth.service, and they're nowhere to be found. Absolutely no feedback on loading firmware. I tried placing the firmware files in a few of the standard locations, but it doesn't seem to improve anything.

Yes, Ubuntu 20.04 is a bit old, but it's still supported, and upgrading in my use case is a major undertaking (and I sometimes need to use “legacy” software which is increasingly difficult to get working on newer distros). I guess I could try booting a newer distro on a spare computer sometime and see what messages or behavior I get on it.