I think just doing files and then syncing the files with another solution it's okay.

For example my local apps: Synthing syncs the files between my computer and phone for Note taking(just markdown and org files) obsidian on my phone, emacs/vim on my PC. Todo and reminders: org mode in emacs (desktop) orgzly on mobile. Password manager: KeePassxc desktop, keepassdx mobile. Calendar: just sync the ics file. Photos: just sync files use the default app. I can continue with this with every app, I don't know why people overcomplicate things

This is more or less what I do too. I sync my whole /storage/emulated/0 on Android, which gives me Photos and Downloads etc. to my laptop. I also put Syncthing on an always-on tiny computer at home so if either laptop or phone is off, I can still sync from the other one (so that little home computer is my "cloud", didn't require anything more than plugging in eth and running syncthing).

Syncthing uses "disovery servers" so no need for public IP's or wireguard or anything like that (you can set up your own if you don't trust syncthing https://docs.syncthing.net/users/stdiscosrv.html but they're only used for that discovery part, which is one of the main hurdles when you start thinking about peer-to-peer systems).

(However, I use Fastmail's calendar, for handling invites and since it keeps my subscriptions up-to-date. Considering the move from bitwarden to keepassxc.)

The problem is that this has effectively no conflict resolution. With naive file-based sync the best Syncthing can do is save both files. Then you are stuck merging yourself. Maybe if all of your devices are reliably online and you only use one at a time. But eventually you get a delayed sync resulting in a state fork and you end up with a mess.

For photos and some other type of data this likely isn't much of a problem. But for more complex data it definitely is.

This is the reason why I'm reading this site - this is such a brilliant idea, super simple and without any vendor lockin at all.

What do you use to integrate ICS into your phone's calendar. This is what i'm suck on. Apps like icsx5 are read-only for ics

I second Syncthing, it’s amazing!

Been doing this for years. It's so utterly amazing and effective.