Well, It is hard to know what is happening without more information. It seems you are applying to a right amount of jobs, it could be that maybe your CV doesn't stand up among other CVs. First thing I would is to improve the CV somehow, try to get feedback from recruiters or other people with experience looking for jobs. It must show you have built something by your own, so you can work on something related because you have already probe you can. If you don't have anything, them start spending sometime working in a pet project and put it open source in GitHub.

Other thing it can happen is that maybe you are not applying to the right places with the right CV, for example it doesn't make sense for me to apply to companies in france with a CV in english, but I would keep my LinkedIn in english. If you are looking for a job in London them you need to now the local websites the recruiters use for this. The are different per country. Do some research on this.

About sponsorship I think this could be the key factor too. I think it is almost impossible for a company justify a VISA for a junior profile. So first you need experience in your local market in order to not be a junior developer. If you want to do something abroad you might want to search for summer interships, summer camps or similar. But don't expect to make money with them, they barely cover the costs.