The important step is to solve the build issue, which will be in how the Dockerfile is constructed.

Can you share which app you're trying to package?

Stick with it : it can be a frustrating process solving the build issues, but once you have success, it's all worth while.

in terms of my issues so far: as a complete layman to all of this, i spun up a VM on ubuntu, installed docker desktop and the cloudron CLI. i installed the cloudron build service app and the docker registry app on my cloudron and entered my credentials in the cloudron settings, as well as editing the /app/data/docker.json file to input the correct details there as well.

i then attempted to build an app and it gave me an error stating the app build failed and inevitably when i tried to install the image, it gave me a 404 although it seems there are some failed instances when i login to the build service online. hopefully this makes some kind of sense, haha!

in terms of a UI to simplify the process, perhaps there could be an additional app on the cloudron store that utilises both the cloudron build service and private docker registry apps to upload, build and install a properly packaged app from this link or self-packaged app, without needing the end user to interact with the terminal?

apologies as i am very out of my depth here haha.

As @girish says, I'm not sure a UI is possible, but maybe you have a good idea.

Actually constructing the Dockerfile is the hard part.
Constructing the CloudronManifest.json is not too difficult from the docs.
Once they are done, I use this little script in Terminal in the folder containing Dockerfile and CloudronManifest.json.
Nothing clever about it, just removes some of the drudgery of terminal commands.
Call it what you want : buildscript.sh ?

#/bin/bash
docker build -t $1 .
docker push $1
cloudron install --image $1

Use it like this :
./buildscript.sh <docker-repo-address>/<app-name>:<app-tag> where

• <docker-repo-address> is where you hosting your docker images (maybe docker hub or a private docker repository : I installed DockerRegistry from App store, so it could be 'docker.mydomain.com')
• <app-name> : whatever makes sense to you
• <app-tag> : optional, just some suffix to distinguish versions of built images
  So it could be :
  ./buildscript.sh docker.mydomain.com/myapp:v1

And of course, prerequisites before any of that are :

• install docker locally and log in to your docker repo
• install cloudron CLI and log in to your Cloudron instance.

Hope this is not too basic.