Hello and thanks for the PR.
First, may I ask how much of it is generated by AI? I am asking because there are some patterns, which are quite typical to AI.

Regarding the approach, I think it is quite different from what is asked in #4761 where the idea is that when accessing a given feed individually, the default sorting should be a function of a preference defined for that feed. Likewise at category level (which can be done in another PR).
Similarly, there is also a wish to allow different default viewing preferences per feed (for another PR).

And indeed, I do not think it make much sense in the same view to mix various sorting orders.

1. I would suggest to replace your new Sort feeds drop-down menu by an option in each feed. The menu does not scale well to many feeds anyway. The preference is to be saved in the attributes of each feed.

2. Drop FreshRSS_Context::$local_feed_sorting and use instead $feed->attributeString('default_sort')

3. This also makes the CSS changes unnecessary

4. The option allow_local_sorting can be removed

5. I think all the changes in FreshRSS_EntryDAO can be dropped (some of it can maybe be discussed).

6. Add instead some minor logic (maybe in FreshRSS_Context::updateUsingRequest()) when landing on a given feed to use the feed's (or category's) preferred sorting order, except when the user overrides the sorting order from the menu. Similar idea as the state_forced_by_user section.

7. Introduce a secondary sorting order preference in configure/reading to select what the secondary sorting criterion should be when sorting by feed name (can be done in another PR).

I realise that it will make this PR quite different from your first version, and sorry for that, but I do believe it would address a more common use-case and be easier to integrate to the rest as well as maintain over time. I hope it can make sense to you as well.

I will make a few more minor reviews inline.

@PeterVavercak Tests welcome if you are around, in particular regarding paging (i.e. autoload of more articles)