Hi, I think you are right with the permissions problem.
I have made a lot of tests. I am use to work with stocking all app installer on a nas. I have ever noticed problems with some apps which need to be copied on the local drive to avoid installation problems, when installer is running directly from shared folder.
This problem was for local installation on the computer, but I give it a try since I was saving zenphoto on the nas, unzip it on the nas too, before uploading them via my ftp computer's client. And now, bootstrap's theme option tab is back ! But slideshow is still broken.
I often got this warning "Your server software has changed from Apache/2.4.25 (Debian) to Apache.
The script SIGNATURE_HASH has changed."
About UTF-8, the setup is showing this warning:
=======
The Zenphoto filesystem character define is UTF‑8 [no test performed]
Warning!
Setup did not perform a test of the filesystem character set. You can cause setup to test for a proper definition by creating a file in your zp-data folder named charset_tést and re-running setup.
If your server filesystem character set is different from UTF‑8 and you create album or image filenames names containing characters with diacritical marks you may have problems with these objects.
Change the filesystem character set define to
UTF-8
===
An "éëèàd" album folder created via ftp is seen in the web gui "éëèàd".
An "éèàt" folder created via web gui is seen "---t" in ftp folder.
A user of the same host provider seem to had a similar issue (with another cms), but I do not understand how to use the solution, here is the information : https://forums.ouvaton.coop/t/utf-8-dans-phpmyadmin/2050
zenphoto is not installed on the root, but in a subfolder (if the information is important).
Another experience: I am installing zenphoto on a second account at the same provider with a separate database. I can give you access. This time I decompress zenphoto on the computer which hold the ftp client, and install it at the root of the web server.