First take some time to actually define the lifestyle you want. It’s very easy in today’s world to get tunnel vision on your career. But once you have financial stability more money doesn’t necessarily make you happier. Trying to move up the career ladder could prevent you from enjoying life. That’s where the saying “money doesn’t make happy” comes from.
But if advancing is important to you there are still ways to achieve this. Consider moving abroad for a few years. Especially the middle east has ton of good job offers and since many people you will work with there aren’t English native speakers your pronunciation shouldn’t hold you back. UAE, Kuwait, Jordan, Bahrain all have a very vibrant expat community. They are more likely to value your experience and offer you a higher position. Then after 2-3 years you can go back with a stronger CV.
Or you can consider picking up a remote job, move to a tropical island and enjoy a more relaxed life. That’s what I did (not as a programmer but still remote work). A salary that barely let’s you survive in the west let’s you have a very comfortable lifestyle. You only have to consider the visa issue but for most countries that means just leaving for 1-2 days every 90 days. And with the extra spare money taking short flights/vacations is easily doable.
Both option obviously depend a bit on your social life.
I only have very limited knowledge about programming. But I do know that some languages are fairly new. So you switching around isn’t necessarily bad. Just focus on something that’s fairly new and then you are on a level playing field.
And if you haven’t done so yet. Spend a few bucks on a professional CV writer. If your interview rate is so low there is a good chance your CV is bad. The job market is crazy at the moment and getting tons of rejections isn’t uncommon. But with 20 years of experience it shouldn’t be that bad.
Head over to the website of the company go to the about section and read about their values. They usually list something like teamwork, communication, working autonomously, speed, or quality. You pick 2-3 of these values and that’s what you talk about when they ask about yourself.
For the actual technical part it’s hard to prepare for. Most people don’t actually care about you being perfect but just want to see if you actually are familiar with what you said you are. So as long as you have an idea what you are talking about you will be fine.
Even if you don’t know the answer, just come up with something that could work. Don’t just say you don’t know. Explain your train of thought as to why your solution could work. And any other ideas you might have.