I did had the same issue with snap under ubuntu 22.04 install on an old machine. . And as you must have figure since snap work in sandbox mode it cannot access the sonoff dongle on /dev/tt0 . So my only choice is to REMOVE snap HA. And tthe success installation road map I followed is this:
1- go to Installation - Home Assistant and select Generic x86-64 - Home Assistant
2- Then skip the first few step and go where it says Install Home Assistant Core near the bottom of the procedure.
3- Use terminal and Install dependencies with command line provided in the text.
I had difficulty in this step because some dependencies did not install.
Checking the error message I did add the recommended package so that repeating this command worked. It might be different for you so check the error is the key.
4- Create an account
I had difficutly with the following step mainly because the groups dont exist in ubuntu 22.04 . Only need to create the three groups .
"sudo useradd -rm homeassistant -G dialout,gpio,i2c ¨
5- Create the virtual environment
6- And lastly run hass
It took a while for the hass to come back. I finally realized that it was the server running accessible on
http://localhost:8123. or on my local wifi as
http://X.X.X.X:8123 (replace X.X.X.X with your machines’ IP address).
I plug the sonoff dungle and restarted the machine then HASS server in terminal as follow:.
sudo -u homeassistant -H -s
Then as explained by sonoff for the zbdongle-p here https://sonoff.tech/product-review/sonoff-zigbee-3-0-usb-dongle-plus-tutorials/ . Sonoff Zigbee 3.0 USB Dong - /dev/serial/by-id/usb-ITead_Sonoff_Zigbee_3.0_U appeared after selecting ZHA . The I selected ZNP for configuration.
The first device I added was a sonoff ZBmini switch it appeared as soon I pressed the configuration button.
The second device was a sonoff SNZB-03 motion sensor . It did not pop out. So first go to setting/integration and get the ZHA device addition. A window appears waiting for pairing. Then press the pairing mode with your sensor close to where you want to install it. So that the newly zigbee coordinator you just install find the best route to reach it.
Hope it helps