Looking for Zettelkasten software meeting certain criteria

Recently, I realised that my heap of notes has grown too big, difficult to handle and includes notes stored in various formats. Looking for ways to escape from what is gradually turning into hurt locker, I read about the Zettelkasten approach and found the idea interesting and worth trying.

Having tried a few pieces of Zettelkasten software, I can say that I am not fully satisfied with any of it.

The closest candidate is Zettlr. The note database is stored as the set of tagged and linked md-files. The only thing I dislike about Zettlr is its being a Javascript Electron-based software. I just don’t like this kind of programs (I am not explaining why here, because I don’t don’t want to waste your time). Also, it has certain limitations, for example, inability to export selected list of notes (to be fair there is a very inconvenient workaround; the lead developer promised to implement this functionality, but you know how it goes «We shall do that, but only after we do some other things, that requires time…»; well, that is generously given to the people for free, so no complaints, but a limitation remains limitation).

There is this software called Zkn3. The interface is a bit (over)complicated (ideally, there should be no need to use mouse at all while taking notes), but I could live with that. The deal breaker is the fact Zkn3 stores notes in its own format (and people report that transferring the whole heap notes into another formats is problematic). It means you are tied to this software. No good thing.

I tried a few more but spare you from reading too much.

Here is the list of criteria, the ideal software should meet (of course, from my own perspective only):

1. to work with notes stored separately in form of md-files or some other mark-up text format (I wonder if it can be LaTeX, which I like enormously).
2. to store tags within note’s body.
3. to be written in some language designed for creating programs in the first place, not Javascript or some thing.
4. to be «serious software» (by this I mean it is not to be developed by one person who, as of tomorrow, may jump to conclusion that maintaining it has become way too heavy burden). Surely, there is no way to guarantee this, but I am talking about reasonable expectations.
5. to run on various OSes (Windows, Linux, Android in my case).
6. to be an off-line tool.

Like every one else on this planet I would prefer open source software or, at least, freeware, but I don’t mind to pay certain amount for some thing worthy.

I shall be grateful for any suggestions.