Okay, all's working now. I think the 503 error I was getting was due to a server issue from Azure. So I deleted everything and started afresh, only this time, I didn't use azure-cli. I created a new Web App, searched a bit and found deployment sources. I chose Bitbucket and connected to the repo. I then synced it after installing composer as an extension. I tried the Command tool from azure, but that gave me 0 helpful output, so I used Kudu, another Azure tool (Debug Console). I changed the perms for the directories you told me about, and I generated a key via artisan from there. I updated the vars in app settings and tried the website. It gave me
ServiceError: Unable to boot ApiServiceProvider. I added APP_PREFIX=api in my site vars and boom. It worked.