Immich all the way. It is very similar to Google photos in terms of UI and features and is being actively developed. You can create shared albums with unlimited contributors and also share an album by its link.
I have used Nextcloud before, but the feature set (even of the memories addon, which is supposed to be better than the default photos app) is severely lacking and Nextcloud is incredibly slow compared to immich.
Assuming it's a 4, you could probably use LibreELEC. There is a plugin for moonlight game streaming.
Kodi, a very popular and highly extensible Media Center which acts as the GUI of LibreELEC, can play just about any media.
Airplay seems to be supported as well.
There is a plugin for Netflix, however note that you will be limited to 720p since you can't use widevine levels above l3.
I am not advocating for the "alternatives" (i.e. Instagram and the likes), however I think banning a Chinese PSYOP indoctrinating a whole generation with far-right ideas can only be positive for society. Hopefully the EU does something similar.
While it does not answer your question directly (sorry), my suggestion would be to just use Firefox for everything. Setting up PWAs in Firefox requires a small amount of preparation work, but once the extension and runtime are installed it's all pretty smooth.
