SpicySquid

What's the use case? Is there a reason that the disk is not unlocked at boot/login?

I think any distro will do really. I'd go for something that is friendly to new users, if you're not very familiar with Linux in general. For example: Linux Mint. Here is an example on how you can get your installation setup easily: https://www.youtube.com/watch?v=IyT4wfz5ZMg

Regarding your Valve Index. It will likely work, but don't expect it to be very easy to get it running well. I'm currently on Arch Linux with red team hardware and a Valve Index. For example, you will need to ensure the udev rules are set properly: https://github.com/ValveSoftware/steam-devices. New issues occasionally arise, see: https://github.com/ValveSoftware/SteamVR-for-Linux/issues. Currently, it's not switching audio devices automatically, so I use pavucontrol (with PipeWire) to switch that manually.

Oh I didn't know that yet! Amazing stuff.

You're in luck. As far as i recall wincompose is inspired by Xorg's Compose feature (https://github.com/samhocevar/wincompose?tab=readme-ov-file#features). Depending on your installation you can toggle it via some settings, or by running: setxkbmap -option compose:ralt

I always find the book useful for this stuff: https://wiki.archlinux.org/title/Xorg/Keyboard_configuration#Configuring_compose_key

I have been in the same spot. Good to read that I've been able to help out. Have fun with this in combination with your gaming!

I use a gaming-mode for that. Like this:

# Create a gaming mode
mode "gaming" {
    # switch to workspace
    bindsym $mod+1 workspace number $ws1 ; mode "default"
    bindsym $mod+2 workspace number $ws2 ; mode "default"
    bindsym $mod+3 workspace number $ws3 ; mode "default"
    bindsym $mod+4 workspace number $ws4 ; mode "default"
    bindsym $mod+5 workspace number $ws5 ; mode "default"
    bindsym $mod+6 workspace number $ws6 ; mode "default"
    bindsym $mod+7 workspace number $ws7 ; mode "default"
    bindsym $mod+8 workspace number $ws8 ; mode "default"
    bindsym $mod+9 workspace number $ws9 ; mode "default"

    # move focused container to workspace
    bindsym $mod+Shift+1 move container to workspace number $ws1
    bindsym $mod+Shift+2 move container to workspace number $ws2
    bindsym $mod+Shift+3 move container to workspace number $ws3
    bindsym $mod+Shift+4 move container to workspace number $ws4
    bindsym $mod+Shift+5 move container to workspace number $ws5
    bindsym $mod+Shift+6 move container to workspace number $ws6
    bindsym $mod+Shift+7 move container to workspace number $ws7
    bindsym $mod+Shift+8 move container to workspace number $ws8
    bindsym $mod+Shift+9 move container to workspace number $ws9
    bindsym $mod+Shift+0 move container to workspace number $ws10
}

# Enter the gaming mode when a game is started
for_window [class="^steam_app_"] move to workspace $ws10; workspace $ws10; mode "gaming"
for_window [class="^hl2_linux"] move to workspace $ws10; workspace $ws10; mode "gaming"

This automatically moves (most) games to workspaces 10 and switches to that workspace. This allows me to use key combinations that would otherwise be used by i3.

I think that should be possible. You'll likely need to get Jellyfin running with that cloudflare tunnel. There are probably alternatives to cloudflare tunnel as well, but I'm not very familiar with it. I believe there are some limitations with the tunnel, so you will have to check that out. Otherwise there should be no issue.

Dozens of GB sounds like there's a lot of media files to me. I'd not share that via Syncthing. Assuming that is correct: Wouldn't a media server like Jellyfin be a better fit? Or if it's photos, I recommend Immich. Note that Immich is under active development and should not be your only place to store photos.

I think self-hosted cloud is a vague statement, but I think with your network infrastructure you will be limited in what you can do. I think cloudflare tunnel could be a good option for getting the device available online.

Then the self-hosted part. There are so many things you can look into. You can run everything in Docker, install the software you want directly on your laptop, and much more.

You'll likely also need a reverse proxy. Can use nginx proxy manager, traefik, or something similar for that.

What are your goals with the self-hosted cloud? That would help you in making it easy to find resources and others here to give you advice.

Edit: typo's