Blogging about stuff you are learning sounds like a great idea. Don't write for anyone else but initially write for yourself. If you write content that is useful for yourself eventually others will find it useful too.

The thing that somehow keeps me from blogging more is that I want to learn/blog about so many completely different topics that feel totally unrelated. Like programming native guis, meditation, cycling, software project management, devops, monitoring,Buddhism,...

So many topics that I feel don't belong on just one blog. I don't know if I should start multiple blogs or use categories on just one site or something else.