Virustotal.com

I have a PWA (Web App) created for this website on my home screen. I always check downloaded APKs by uploading them here.

It's smart. It does not always require you to upload the apk. 99% of the time, the APKs from Mobilism are already uploaded and scanned there by other users. In that case, the website simply checked the file hash, skips the upload and shows the scan results.

As for the scan results themselves, I'm not an expert. Maybe others on this thread can help you there.

Unzip the apk and look through the filesystem. Some malware will be obvious.

Install the APK on an android development vm and use it for a bit. Maybe give it a week to start showing ads and stuff. Maybe try capturing network traffic and try to determine if it's legit.

If you don't need network access use netguard or some other local firewall to disable network traffic for the app and just use it normally

Back up your important stuff and be ready to wipe your device if you notice any bad behavior. Of course some malware doesn't show itself at all, so you may never know.

There are plenty of things that scans will not pick up that you still likely don't want your apps doing.

However an alternative app store I use is F-Droid. Which only hosts apps that are open source. This means that it is significantly less likely that anything bad will be on the apps. Since the source code is available for anyone to review. It also means that everything on there is legally free anyway. 😀

I downloaded an apk from [random sketchy site]

🙄