Okay, managed to clear everything up with this. This feels extremely specific to however I messed it up, but I’ll try and outline what I did just in case it’s helpful to anyone.
I corrected the permissions as listed by @Mr_Coder above, then went about removing the symlinks I added for the node directories using unlink. I then uninstalled and reinstalled node using:
sudo apt-get remove nodejs npm
sudo apt install nodejs
sudo apt install npm
Then I had to update npm, using npm install -g npm@10.2.3.
I went to try and restart ghost again at this point, but needed to update the CLI (since I switch the node version) and some of the supporting packages using the --force flag on ghost update.
From there, ghost said it was running, but still wasn’t resolvable, giving me a 502 error. mysql seemed to be running, but I saw here that node 18 doesn’t like ipv4, so I updated my config file to specify 127.0.0.1 instead of localhost, and blam, back online.