Companies have an existing stack, and they don’t want to spend time having to train you, if they simply can buy the skills on the market place.
Training will only happen if a company switches, and you are already employed. Don’t expect anything else these days, unless you are willing to work for an organisation that expects you to stay for decades (think government, or working on Cobol on an IBM mainframe).
It’s simply what it is. So you need to provide you have experience with a specific stack. You can start an open source project scratching an itch, to demonstrate you have what it takes. Or join a project you’re passionate about and start helping out. Providing pull requests, fixing merge issues, that kind of thing.
You can also volunteer at a charity for a while and that way gain skills. It will be self-driven, training someone is a lot of hard work, and the best techies have way to much work to do that.