Twenty years ago, when I was just starting my professional career, I would probably agree with Paul and say: "Go to universal naming conventions!". :)
Today my answer is different. Accepting decent naming conventions is challenging, even if you are dealing with a single programming language. Having universal conventions for several languages / frameworks is a noble goal and an excellent brain teaser, but in general I do not consider this possible. The syntactic and lexical rules of different languages / frameworks are too diverse for "one size fits all." In addition, the set of languages / frameworks used can change at any time, and the corresponding adjustment to your “universal conventions” can be prohibitively expensive or prohibitive.
Therefore, I would recommend focusing primarily on solid and decent conventions for each language / structure (or for each group of languages / frameworks that are fairly similar - for example, C and C ++). One of the good results of this approach is that projects in which only one language participates should adhere to a set of agreements that do not look “foreign”.
Having said all this, I believe that some conventions may be common to all the languages / frameworks involved, without becoming too “alien”. Moreover, such a thing as vocabulary should be common to the entire project. These are mainly semantic and lexical rules, of course; but even some syntax rules can also be universal. For instance:
Lexical rules for entity names (for example, "always use singular nouns").
Lexical rules for acronyms (for example, "use only well-known acronyms").
Syntax rules for compound names (for example, "always use a common and then a specific sequence").
The above examples are, of course, simplified. But I hope the idea is clear: any general agreements can be general, but it will always be just a subset of all the conventions that you need.