Can't find startup disk on MacBook Air after doing a Hard resert.

Trying to sell a Macbook Air 2017 (using Intel) with MacOS Monterey and was unable to erase all data and factory reset it the usual ways, as there was no option in settings or applications to do this. An Apple Forum said this was a common issue and people had resolved it by restarting the computer into recovery mode (using Command + R) and erasing the disk in disk utility.

Tried this but now when the computer restarts it goes to this screen:

Ran first aid on all disk utilities, but there are no errors, disk utility looks like this:

Tried to reinstall macOS High Sierra, but keep getting the message "recovery server could not be contacted". Screenshot below:

When I click select startup disk from the Apple Menu, it doesn't give me a disk option to select. See screenshot below:

Any help would be greatly appreciated! I'm not very tech savvy and am a bit lost.

[Re-Titled By Moderator]