This is inconvenient in some ways, but at least it is sort of privacy as good as it gets while still being able to run official apps when I need them at home.
To de-google the phone, I use F-Droid as primary App store, Aurora as fallback for non-f-droid Apps and as a last resort Obtainium to install Apps that are not in these stores.
The only google App I really "need" (kind of) is the Camera App, which is sandboxed via GrapheneOS Storage Spaces and without Network permission (why would a camera need internet?).
To backup my phone, I use the integrated GrapheneOS Solution (seedvault!?) for storage and apps, immich for Photos and MyPhoneExplorer for Contacts.
Sometimes it is a bit hard to find good apps for specific purposes, so for everyone interested, here is a list of Apps that I personally use or have used.
Newpipe - Youtube Client
Audiobookshelf - Audiobooks
Voice (PaulWoitaschek) - Local Audiobook Player
Substreamer - Music
DSub - Music (alternative)
VLC - Video-Player
Organic Maps - Google Maps alternative (not as good)
PDF Doc Scanner - Open Source Document Scanner
Wireguard - VPN
Immich - Photo Backup / Viewer
LocalSend - File Transfer
K9 Mail / FairMail - Email Client
KOReader - Ebooks
Binary Eye - QRCodes and Barcodes
Pure Todo - Self hosted PWA PHP Todo List
Signal - Messenger
Open Camera - Open Source Camera App