No, but you do have to go into settings to allow apps to be installed from elsewhere. More often than not, you can just wait for the prompt (when installing something directly or when installing F-Droid) to allow installation from those sources.
I use F-Droid for most apps. If I need something from Google Play Store, I download an app called Aurora Store from F-Droid. It's an alternate Play Store frontend that:
Lets you download and update apps from the Play Store without a Google account
Is actually usable to find stuff, unlike Play store which is all suggestions (ads), "recommended for you" (ads), and ads.
You can also download apps directly from the creator as .apk files. A lot of FOSS apps will publish APK releases on Github.
? Depends on the app? As the other commenter said you can also install an alt app store. You can also just download the apk directly to the device and install it.
I use mine solely as an ereader so the only apps I have installed are Firefox and mihon (a tachiyomi fork for reading manga).
Games kind of suck on the panel tbh, anything that needs a lot of motion like youtube is similar. It works but it’s garbage compared to oled/lcd
Well, since you're only using it as a reader rather than a general purpose device, the only difference you'll notice is paid apps not really being available. Like, moon reader+, which is very popular, you end up not having access to without Google's crap. But there's plenty of others that are damn good, so unless you're dead set on one specific paid app, I'd say it isn't worth it tbh.
I have the play stuff active on my little boox specifically for moon reader, which I would much prefer over the next best options for my use, but it isn't an absolute dealbreaker tbh.
Fdroid has several open source options for reading, and they're all at least decent, with librera and fbreader being superb (imo). Both can be found as apks elsewhere, if you go digging, but fdroid is easy to use, so why bother?