OpenCore Legacy Patcher's (OCLP) instructions are somewhat wanting. On a trip, I got a prompt that a new update to OCLP was available. Generally you don't need to install updates unless you are planning to upgrade to a new macOS that that update provides support for but, knowing me, I install them all.
The OCLP updates install automatically after you accept them but I was too aggressive. I got a prompt that something couldn't install because something else was already in progress. With no guidance from OCLP, I clicked the "Retry" button.
A prohibitory symbol, which looks like a circle with a line or slash through it, means that your startup disk contains a Mac operating system, but it's not a version or build of macOS that your Mac can use.
The MacBook wouldn't boot. Basically, the on-the-fly OCLP firmware patches weren't being installed and the MacBook Air 2015 wouldn't boot Ventura.
Being out of town, I didn't have the "magic" USB drive that I had used to install OCLP. Perhaps, with that I could have repatched the firmware.
Anyway, I had a MacBook brick for the rest of the trip. Thankfully, I had brought a Windows laptop as well.
Back at home, I still couldn't figure out how to repatch using the USB drive.
Finally, I just did a hard factory reset (archive.org) on the MacBook and rebuilt it. At least that was good practice and a check on my documentation.
There are lots of links on Google about how to reset a MacBook but they are usually telling you how to erase it. The above linked lifewire.com article will let you reset a bricked MacBook over the Internet. Pretty cool.