If you just want to control switchbots from HA, and if you have a way to communicate to switchbots via bluetooth, then no - a switchbot hub is not required.
Also you could even roll your own hub, if that is your thing.
Search switchbot here and you can find some users using an ESP32 (which has wifi and bluetooth) that bridges switchbot controls through MQTT. A fairly popular thread IIRC.
Yes, you can use Switchbot to open your garage door without requiring a switchbot hub.
I have a Switchbot in use here with HA running on a Pi 4. I never could get it working using the Pi’s internal Bluetooth and just ended up using a USB Bluetooth dongle - in saying that, it could be a very simple thing, I never really bothered delving into it because I have several Bluetooth dongles lying around so it wasn’t worth my time.
Additionally, I did end up with the Bluetooth Dongle connected via a 1m USB extension as I found Zigbee was interfering with the Bluetooth on rare occasions, but simply putting both dongles onto USB extensions was enough to resolve my issues - so if you’ve got a Zigbee Stick in your Pi its something to be mindful of.
(i didn’t tested in 2022.11) in 2022.10 it is now fast to execute commands but unstable because the bot goes unavailable after a while… i reverted back to 2022.6 + switchbot_press