I'd recommend setting up a GitHub profile and developing some personal projects on there, and try to get some experience contributing to other projects (even if they're just simple first PRs). Make sure you include this on your resume, it's a great talking point for juniors to show you're passionate and have concrete examples of your code in the wild.
Also set up a LinkedIn profile (fleshed out as best you can) and start adding people at companies you're interested in. DM them asking for advice, most people are lovely and want to help. While LinkedIn is horrible and needs to die, it's still used heavily by the tech industry and you'll find every tech company and recruiters on there.
WhatsApp has been exploited before with a zero-day, check the Complaints section in this link:
https://en.m.wikipedia.org/wiki/Pegasus_(spyware)
The reality is WhatsApp and Signal will continue to be high-value targets for exploits given the number of users, cloud infrastructure reliance and promise of secure communications, so it's a wise idea to avoid them for defence matters.