Installing UIBuilder failed with from within nodered with Palette installation as well with "Manual installs and other versions" as posted on Github page.
I've just checked and I can't find any indication that any of uibuilder's dependencies would try to install LevelDown. Double-checked against several installations as well.
So as far as I can tell, something else is causing that.
I would suggest starting by finding out what installed package(s) are trying to use leveldown.
Oh, and you really shouldn't be installing Node-RED nodes with SUDO. That indicates a wrong installation.
And reify? What is that doing in there? Again, nothing uibuilder does involves it.
A bit more explanation of what might be going on. When you run npm install it first checks that everything else specified in package.json is as it should be, so it is probably that operation that is failing. You can check that just by running npm install
$ npm install
npm ERR! code ENOENT
npm ERR! syscall open
npm ERR! path /home/pi/package.json
npm ERR! errno -2
npm ERR! enoent ENOENT: no such file or directory, open '/home/pi/package.json'
npm ERR! enoent This is related to npm not being able to find a file.
npm ERR! enoent
npm ERR! A complete log of this run can be found in:
npm ERR! /home/pi/.npm/_logs/2023-03-30T10_15_56_431Z-debug-0.log
After some searching about possible fixes ... I'm going to restart the RPI
Thanks for the moment
... includes the Raspberry Pi OS-packaged version of Node.js, but does not include npm
Since npm is (usually) required, what would a subsequent secure installation of npm be like?
That refers to the packaged node red in the pi os repository. If you use the recommend script shown there then it should install everything you need, apart from build-essential, git and curl which you should install first as described there.
Clean RPI/OS/NR/MQTT with on top UIBuilder installation and everything is OK
Now NR/ui is running with the first nodes in production (on port 1880). Next will be a dev part to use UIBuilder with separate setup on port 2000 (as described with the other discussion).