Alright, today I finally managed to install flarum on my webhost with no SSH access by using this tutorial: https://discuss.flarum.org/d/2047-how-to-install-flarum-on-localhost-and-shared-hosting-tutorial/15
However, I quickly learned that there is a problem: How am I supposed to install an extension now? The folder itself is gone since it is normally done by using composer. But as I said above, no SSH access on my webhost.
You probably can guess my problem now. Would it work if I, like in the tutorial, download my current flarum installation to my computer and simply install the extension with composer there, and then reupload everything again? Or are there changes to the databse itself when installing an extension?
Or is there even another solution?