Good list but let me respond to a few of those.

Calendar -NextCloud is needed to sync. On my Android I use simple calendar and the dav5x app connects it to my NextCloud to sync to it. The stock Calendar syncs to NextCloud on my iPhone.

Contacts - same exact setup as how I do Calendar. NextCloud is needed to sync. On my Android I use simple contacts and the dav5x app connects it to my NextCloud to sync to it. The stock contacts app syncs to NextCloud on my iPhone.

Maps - I absolutely loath organic maps. It never worked for me. I would put in a street name and address and it would never find it. I need stuff that works. So it's Magic Earth most of the time and Google Maps if I'm really serious about getting somewhere and scared to get lost. Like if I'm in a sun down town or some shit like that.

Weather - I also use Geometric weather. Fantastic app!!!

Google Play store - When I first started degoogling, I tried to completely cut out the play store but then some apps that I paid for would never work. And they refused to accept any other form of payments. So I use the play store to download certain apps and then I block it with afwall+. I mostly use Obsidian and F-Droid

Google authenticator - I use 2fas. I like the browser extension and it just works seemlessly between my android, iphone, and desktop. It's also now recently been open sourced.

Google messages - I also use simple sms. I really like the simple suite and how simple it is. I even use their dialer and gallery.

Gboard - is probably the very last Google app that I'll get rid of. I've tried all the open sourced keyboards and none are as good. But I do have afwall+ blocking all outgoing connections on my Gboard. Gifs don't even work.