Honestly, if your willing to learn to use LibreOffice, it’s way more powerful than OnlyOffice. It took me a minute to get used to it too, but once you do, it’s pretty awesome. And if your worried about UI, you can change some of those things in the settings, like you can make it have a MS-style ribbon at the top. If I were you, I’d spend two weeks trying LO, I think you’ll get used to it pretty quick

As far as sandboxing goes, there’s always Island, Shelter, and Insular, which all leverage the work profile function in android to give you a privacy sandbox of sorts. Problem is, your phone still uses Google Play Services at the system level, so any tracking data being sent through it still gets where it’s meant to go. That being said, leveraging the work profile gives you an extra VPN slot, which can be used with either an always-on VPN, or that slot can be filled by a firewall, something like RethinkDNS or Netguard. Invizible Pro is a good option too, it can route all traffic through TOR, has DNSCrypt built in, and has a firewall (though I’ve never had success with using it). One thing to consider is that Android has been caught sending tracking data around the VPN tunnel if I’m not mistaken.

As far as location spoofing, faking logs, etc., I’m pretty sure you’d have to be rooted to do that kind of stuff with any real efficacy.

The real answer is root + microG + AFWall + any other privacy controls you can get your hands on (I’m a huge fan of XPrivacyLua, personally) and THEN consider something like Shelter

The realer answer is don’t use TikTok

Yandex