I've read this question about posting questions for jokes you didn't understand in the english language.
Can I also ask questions about jokes in comics (in the English language) that I didn't really get?
The English Language and Usage Stack Exchange is for linguists, etymologists, and (serious) English language enthusiasts. [At the time of this answer,] questions on the following topics are welcomed here:
• Word choice and usage
• Etymology (history of words’ development)
• Dialect differences
• Pronunciation (phonetics and phonology, dialectology)
• Spelling and punctuation
But please, don’t ask any questions about the following topics. They are out of scope for this site.
• Proofreading ("are there any mistakes?"), unless the source of concern is clearly specified
• Writing advice or critique requests (see Writers.SE instead—note critique requests must meet their criteria)
• "How to improve my English?" (this is not constructive anyway)
• Translation and non-English languages
• Naming, including naming programming variables/classes
• Criticism, discussion, and analysis of English literature
• Jokes that do not rely on the English language
That at least implies that jokes which do depend on the English language are on-topic.
The important thing is that jokes must rely on the English language. In the case of the comic strip about F5 I'm not convinced that it does rely on English. It relies on a knowledge of Windows software.
If one is going to ask about a joke, it's probably not obvious whether it's on-topic or not, particularly if one's first language isn't English. I would suggest that the most appropriate forum for such a question, at least at first, is in chat1. You may well get an answer straight away, or some interesting point may emerge which indicates that the joke may be of more general interest and might actually form the basis of a question.
1 Although anyone can read chat, participating requires 20 rep, which might be gained by just one on-topic question if you don't have the +100 association bonus.