If you don't even have a wallet you can still use this service it provides you one. That is the goal to make it as simple as possible and at the same time you can use your own node and instance with this, without any coding required on our side.
Discussion
The media URL means you have to host it somewhere? Can I host it in my node?
For media you can use any uploader it redirects you do they nostr.build but you can use your own uploader or any premium one.
For personal node: Get the node attach it to the Lnbits. Lnbits should be hosted and maintained in your own server with admin access. Get the API used it as a login key.
Everything is open source!