Exodus Privacy is a good starting point. They also have an app to check your installed apps with.One possible next step could be to install an Android firewall like Netguard or Rethink DNS + Firewall to block unwanted connections. Both don't require root and are well documented.
I'd recommend iodéOS instead of /e/OS as the former is considered a bit more secure than the latter, see overview of Custom ROMs here (summarized from a well known German IT-Security Blog). You can also buy a FP5 with iodé preinstalled.
I have an Asus Eee PC from 2009 running Puppy Linux (as a secondary device).As already pointed out you will need a leightweight distro and desktop environment.
https://distrochooser.de/ (available in English) can help you find the right distro, it takes into account the age of your device, your Linux knowledge, use case and a lot more.
My data is my data. Period. Or at least it should be.Abuse of position as dominant provider of search engine (incl. censorship) and mobile OS.Labour Practice.e.g. https://en.m.wikipedia.org/wiki/Criticism_of_Google
Appologies for my aggressive tone. I really hate these companies / their owners and what they are doing to our society, wellbeing, and humanness. It could have turned out so much different, if not for their greed and egoism!
"NOTE: main server is offline, you’ll see the message that you’ll add a mirror, that’s expected. To make it skip the main server, open repo details and toggle off first collaboraonline.com entry." (https://forum.f-droid.org/t/known-repositories/721)
Ah yes, for a start Tracker Control is even better than a Android firewall. If you don't have F-Droid, an alternative PlayStore installed yet, you can also get it here: https://play.google.com/store/apps/details?id=net.kollnig.missioncontrol.play