Mapping with this app is a lot of fun! Sometimes I just go for a walk and open up StreetComplete to see if I can add some small contributions, like the opening hours of some nearby establishment or whether a given entity is still at the location.
You can also customize what kind of questions are shown so you can skip on things you may not like.
I have used mailbox.org before migrating to my own server. Pretty solid.
It’s kind of broken at the moment, but I have set up duplicity to create encrypted backups to Bacblaze B2 buckets.
Of course the proper way would be to back up to at least 2 more locations. Perhaps a local NAS for starters. Also could be configured in duplicity.
The only smart appliances I have ATM are smart light bulbs. These also partially contribute to saving energy (eg turn off lights when nobody is home / in the room), but even if that is not your priority, you can set up nice automations to soften the light as it becomes darker. I also use HA with Rhasspy to voice-control the lights.
As for fridge contents tracking, I wish there was a usable solution to what you describe. I have tried Grocy (can be integrated with HA), which looked nice, but I eventually stopped as it took a really long time to maintain. After each shopping, I had to input everything I bought (almost an hour usually). Then, each time you use something (eat a bun with some cheese, finish a bottle of milk, open a new sachet of some seasoning, etc), you must ‘consume’ it in Grocy. 99% of the time I forgot or was too lazy (once again, it just takes too much effort) and therefore the stock database was always out of date, making the whole thing useless.
Other things: I haven’t tried yet, but I also want to acquire some cheap sensors for temperature, and perhaps other things that I can’t think of right now. Maybe turn on the AC for a bit when it gets too warm (and somebody is in the room)?