I've used Invoice Ninja for awhile. Works great. Self hosted but not foss.
"Cloud" storage is indeed more expensive. But depending where you live, you count the electricity cost in, and you use the storage 'only' for backups. Maybe it makes more sense to pay for remote storage in a datacenter. Check out Hetzner Storage Box, it's what I use.
If it's still too expensive, maybe ask a friend or family member (maybe someone that uses your media) to setup a nas at their home for backup purpose. (I use this for my media)
Make sure you encrypt your backups if you use a remote location for your backups.
You have to decide what's valuable for you. For me my media is, I can just download everything again, but the time I put in to have every movie the correct subtitles without ads, the correct posters, metadata etc. I value my time, I don't want to do it again if I loose everything.
In my opinion I feel like /e/OS is too bloated and I don't like the iOS inspired theme. If you prefer stock android you should choose LineageOS. BTW there is also a fork of LineageOS called LineageOS for microG, should you need Play Services.
And recently Llama3 and Mixtral!
There are a lot of different methodes you could try. I think the easiest is to connect both systems with a (mesh)VPN like Wireguard, ZeroTier or Tailscale. Then you can simply copy stuff over using rsync -a (archive mode) with a cronjob or using special tools like Borg backup, kopia, etc
I had the same issue with my Anonaddy alias, I just made an alias using my domain name and works fine now. It's unfortunate that so many project are on shithub.
You can use Universal Android Debloater. Most apps have a description of what it does and if it's safe to remove or not. Already debloated a few Samsung phones with it, works great :)
A few months ago I bought a second hand Nvidia Shield TV (€40), flashed LineageOS on it. Very happy with the device, especially the performance.
I use Jellyfin, SmartTubeNext and some VOD TV apps from my country. I've Adguard Home on my Proxmox server (can also be a Raspberry Pi) that I use for DNS adblocking, so we can watch VOD TV without any ads. Works really well :)
We've switched to this from cable TV and my family loves it, we can watch anything we want without any ads and FREE!
Only problem (not for me) is that Netflix doesn't work on it without GAPPS.
Simple for me