I never heard of Cozy, but it looks quite nice. The Self-Hosting Documentation ist a bit lacking, but https://github.com/cozy/cozy-stack-compose contains all required information to set it it up yourself.

I originally used Nextcloud, but it has a lot of features not related to file hosting

Cozy seems to be in a similar situation, where file storage is just one of many features that it provides. If you want just files, it might be the best idea to just use any WebDAV Server or something like File Browser.

phyphox has an Audio Amplitude feature.

basic flyers & ads, restaurant menus

For this sort of things, LibreOffice Draw can be really good. I even used it in the past to create memes.

It supports any ONVIF compatible IP camera as well as USB cameras and the raspberry pi camera module

MotionEye used to be the go-to solution.

I am not sure about the current state of the project (the python 2/3 transition took a long while, there are only pre-releases using a modern python version).

Some people also swear by other measures, like changing the SSH port to something else. Most people end up using 2222 to easily remember. This is borderline useless, as you can see for yourself.

While being useless against a sophisticated attacker, there hasn’t been any bot activity in my sshd logs since changing my ssh port to a different one.

Declaring the use without a paid license as “Unlicensed” is very misleading since the project is also licensed under the GNU AGPL v3.0.