bluetooth keyboard on openbsd

Trying to get a bluetooth keyboard on OpenBSD working, here is the
results.

Getting bluetooth audio working has a useable workaround which many
know about already.

In summary, my attempt fails but below is the info which may be helpful to
others who attempt this.

Options to get a bluetooth keyboard working on OpenBSD?

- [X] Someone writes code to support bluetooth in OpenBSD. Yeah,
that's likely not going to happen (understandably it's not supported).

- [X] Search the mailing list for others having tried this.

I only found this article [1], which looks useful to me.
[1]: https://www.mail-archive.com/misc@openbsd.org/msg175271.html

The author Zé Loff suggests that the Belkin adapter F8T016 can pair
to the keyboard via bluetooth and present the keyboard as a USB
device. Perfect. Sadly, one can't find or buy this anymore anyway
and I can't find a similar replacement. :(

- [X] Try searching the net for a USB device that could do this.

A LLM suggests it's called a "Bluetooth Host-to-USB HID converter".
We need a USB device, which can pair to a bluetooth keyboard and
present the keyboard as a USB keyboard device.

It further suggests the Handheld Scientific BT-500 http://handheldsci.com/kb/
Contacting the company they say this only makes wired keyboards work
over bluetooth, not the other way around! Fail.

Another suggestion online is to buy a Bluetooth keyboard Emulator
from https://shop.intelletto.com/products/bk100. Contacting the
company they say the "BK100 is a slave device and will not connect
to another slave like a keyboard." - so it won't work.

Another suggestion is the Logi bolt
https://www.tumfatig.net/2021/logitech-mx-keys-and-mx-master-on-openbsd-using-logi-bolt/

LLM says::

#+begin_example
### what is logi bolt?

Logi Bolt is Logitech's proprietary wireless USB receiver technology,
introduced in 2021. It's designed for business/enterprise use with
enhanced security and better wireless performance compared to their
standard receivers. It offers:

1. More secure connections (Security Mode 1 compliant)
2. Better resistance to interference
3. Greater wireless range
4. Support for multiple devices per receiver
5. Bluetooth compatibility

It's commonly found in Logitech's business-focused mice and keyboards.

### can it pair to any bluetooth keyboard?

No, Logi Bolt can only pair with Logi Bolt-compatible devices
(specifically Logitech devices marked with Bolt compatibility). While
Logi Bolt receivers do support Bluetooth protocol, they are designed
to work exclusively with Logitech's own Bolt-enabled peripherals. You
cannot use them with standard Bluetooth keyboards from other
manufacturers.
#+end_example

Reading the website
https://www.logitech.com/en-za/business/work-setups/logi-bolt-wireless-technology.html
it says:

#+begin_quote
Our Logi Bolt wireless devices are Bluetooth Low Energy 5.0 or
higher. We actively use all the security mechanisms introduced in
Bluetooth Low Energy Core Specification 4.2.

From a backward compatibility standpoint, Logi Bolt wireless devices
are able to communicate with Bluetooth Low Energy 4.0 hosts or higher
when in direct Bluetooth connection.
#+end_quote

so according to the LLM it won't work. According to it's website
it sounds like it may work. I tried to pair it using solaar on a
Linux PC, but when I try pair it to a bluetooth keyboard (not a
logitech bolt keyboard) it doesn't see it. Fail.