You definitely can. I use GrapheneOS and F-Droid as the app store. I guess the phone itself is from Google but other than that nothing. I even get OTA updates a

You definitely can. I use GrapheneOS and F-Droid as the app store. I guess the phone itself is from Google but other than that nothing. I even get OTA updates asap. I use NewPipe instead of YouTube, my own Nextcloud instead of Google Drive etc.