I believe you forgot to mention one of the most important security features, which is to encrypt your phone.

If you lose it and it is encrypt, nobody can see your photos, personal data, etc, even if they manage to get through your lock screen.
When your mobile phone is encrypted, your personal data is unreadable, so it is useless.

This is a guide telling how to encrypt your mobile phone, android and ios.
Those steps are pretty simple, like going to Settings > Security > Encrypt Device.

https://www.lifewire.com/encrypt-the-data-on-your-android-phone-or-iphone-2377707
https://www.androidauthority.com/how-to-encrypt-android-device-326700/

Additional is avoid using some public wifi, and also if someone will borrow your phone make sure you have your attention because some people may try to open some of the applications in your phone that are private or some confidential such as your email accounts, cryptocurrency wallets, etc.

Avoid trusting anyone with your phone especially if you know that there are important inside of your phone and avoid sharing your lockscreen/phone password or patterns to anyone.

And also if your phone (especially android) has micro sd card, avoid storing some important files here because it's easy to steal it and access your files there especially if they are not encrypted.

It is important to emphasize that if you want to have secured smartphone you need to update it on a regular basis, but this is not something a user can just do like that, it depends on your OS/manufacturer. For example, I have the latest Android OS in my smartphone, and every month I get security/critical updates, but my old phone did not have any of them for years. The conclusion is that if you want security, you need to follow the technology.

Security software is as essential on a smartphone as it is on a desktop computer, but to run them without slowing down phone newer generation processors are needed as well as more RAM (you need to buy a new phone from time to time).

Most modern smartphones have fingerprint lock, facial recognition, and 4-6 number password lock. All this together is very useful for average protection, but fingerprint lock or facial recognition can be abused in at least two situations.

- When you sleep, anyone can unlock your phone with your face or by using your finger.
- You may be forced to do that by attackers or authorities.

In case you have confidential information on your smartphone, the only way to protect them is to encrypt your phone (see a post by bitmover), but it is not something that should be done unprepared.

Being careful with your browsing habits is also a very important thing. If you're visiting shady sites or downloading apps from third-party websites, your device is probably infected already and the tips mentioned above wouldn't be that useful.

I would like to add this from Bitmover for mobile encryption but this is only for Samsung devices.

3 weeks ago I bought a new phone which is Samsung Galaxy A10 it comes with Samsung Knox it's a pretty cheap phone that is why I decided to buy it I have a thread about this here
The Good thing about Samsung Knox it has a secured folder and all files and data are encrypted if someone trying to root the phone the Samsung Knox will not work and you can't able to access the encrypted data unlike the methods provided by Bitmover this one will be much more secure than that.

So if you have a Samsung phone check this list of supported devices and maybe your phone is listed. If you found that your phone is listed update the device to the latest version and latest security patch to obtain the secured folder and put all wallet and important files inside of this folder.

Samsung Knox encryption is poorly secured. Whilst it's better than nothing, don't rely on it for any truly sensitive data.

Why do I say this? The encryption key it uses is not derived from your password or PIN, but is a preset key on the device itself since time of manufacture. If you forget your PIN to Samsung Knox, you can reset it by logging in to your Samsung account. All your data inside the secure folder persists through this reset, and you can still access it all afterwards using your new PIN. This means although the data is encrypted, it is only as secure as your Samsung account login. If you want to encrypt it properly, you'll need a third party app to do so.

Good point but i wanted to add one way to avoid  being scam.

- Don’t click on strange links

To be exact Phishing is one method of hackers and this has been around as long as we have internet.

What they do is to  send email as their trick to e-mail recipient into downloading the attachment (exposing their PC or phone to  the malware), or clicking the link to a website that may be infected with malware, or asks for confidential data and worst even enter and access your phone datas.

So we must be conscious on what links we ate clicking to secure privacy of datas.

Never enter your email passwords to login to random sites.

Never store your card details while purchasing on 3rd party sites.

Don't ever install unknown apps or apps from 3rd party sites.

Keep checking your application manager for App with no name and no logo from time to time,which is some kind of spying app.

Rooting has lot of advantages but if it was done by the person without much technical knowledge then they are breaking the security of their mobile.When our software gets too old and no updates from the manufacturer then its better to upgrade the device in my opinion.

Public charging ports?? What is that?

Do not root? So we should rather trust the devs and creators who love hiding bloatware in their phones? Rooting gives you more control of your phone. If anything it makes it safer. You can block so many things your phone automatically does without you knowing if you root your phone. Look at DNS66 it blocks annoying pop-up ads especially ebooks that normally happen in the background. There other things you can block too that is just one example. Having more control is never a bad thing. Obviously, if you don't know what you doing you have no business in rooting phones to begin with and probably will brick it or worse.