Is this even possible?
You read in the news about companies that sell exploits to governments and state actors on hacking the phones of dissidents and human rights activists. The Israeli company NSO is being sued after claims, which the company denies, over 1400 were hacked.
Are they any meaningful precautions or apps one could use? Why are computers marginally more secure?
Of course cybersecurity for phones is possible. It’s also common. Any phone you buy will, out of the box, have considerably more security than your typical PC. Why would you think otherwise?
And of course there are additional precautions one could take, but what precautions one takes depends on what threats one wishes to defend against. “Attacks” or “hacks” isn’t nearly specific enough.
I’ve got a VPN service on my smartphone that I use on public networks. I’m much more likely to be on a publicly unsecured Wi-Fi when out and about with my phone.
It’s not at all foolproof, though; you still have to connect to Wi-Fi before starting up the VPN, leaving a fairly large window of unprotected access, but certainly better than nothing.
Phone security is better than PC security, because it is a closed ecosystem - the hardware and Operating System is tightly constrained, user access rights are managed, the programming interfaces between the apps and the OS (APIs) are restricted and specified, and (in general) apps are installed via an Application Store that can (but may not) evaluate the available applications for security risks and obnoxious behaviour. Phones also have security features PCs generally do not have - fingerprint scanners, face recognition, PIN codes, etc.
Android is a more open ecosystem, while Apple IOS is more restricted.
However, there are still gaps that can be exploited, and phone OS developers work hard to close them when they are identified.