If by side-loading you mean installing from a ‘non-trusted’ or ‘unofficial’ source (apps other than google play store), then yes, that is the only option. however, this is not much less convient or secure.
There are a few ways to install apps (these should work with any Android phone, not just Grapheneos):
Any non-paid apps on google play can be installed using Aurora Store. supposedly you can use it without even logging in to google account (but i havent gotten that to work). Eg. Facebook
Most FOSS apps will be in the F-Droid repository, and can be installed with the F-Droid app, or other similar apps such as Droidify. Eg. K-9 Mail
If an app is not on the main F-Droid repo, alternative repositories can be added to your F-Droid client.
APKs (app packages) can be installed from the web. this is how F-Droid is usually installed for the first time. Eg. Signal is not available on F-Droid (for reasons)
Basically, if you need a proprietery app like Facebook, use Aurora; if you need an open source app, look for it on F-Droid or download the APK.
There are of course pros and cons of each method in terms of security and convenience.
If by side-loading you mean installing from a ‘non-trusted’ or ‘unofficial’ source (apps other than google play store), then yes, that is the only option. however, this is not much less convient or secure.
There are a few ways to install apps (these should work with any Android phone, not just Grapheneos):
Any non-paid apps on google play can be installed using Aurora Store. supposedly you can use it without even logging in to google account (but i havent gotten that to work). Eg. Facebook
Most FOSS apps will be in the F-Droid repository, and can be installed with the F-Droid app, or other similar apps such as Droidify. Eg. K-9 Mail
If an app is not on the main F-Droid repo, alternative repositories can be added to your F-Droid client.
APKs (app packages) can be installed from the web. this is how F-Droid is usually installed for the first time. Eg. Signal is not available on F-Droid (for reasons)
Basically, if you need a proprietery app like Facebook, use Aurora; if you need an open source app, look for it on F-Droid or download the APK. There are of course pros and cons of each method in terms of security and convenience.