Since you’re now able to see the laptop screen with the monitor connected, try changing the monitor’s resolution and refresh rate to a lower value. Plasma should hide options which are incompatible with your monitor, but maybe it’s not doing that for you. (right click on the desktop and choose “display settings”)
Does the monitor turn on from standby when you plug the cable in? If the monitor has other ports, try those as well.
There’s a typo in the article, it’s ~/.local/share/kscreen
In desktop mode, you can press the Super+P (Win+P) keyboard combination to bring up a menu to choose which screen to display on. Keep pressing P while holding the other key to move forward in this list, then press enter. If you keep doing this, eventually you should end up on an option that includes your laptop screen. Alternatively, you can make Bazzite forget about your monitors by deleting the file it stores screen profiles in, then rebooting: https://ryan.himmelwright.net/post/reset-plasma5-monitor-config/
Don’t know of a solution that does this, but you could solve it with a two-step process. First, rsync the files to the server as-is, then use a background job on the server that converts lossless to lossy every hour or so.
Storage is really cheap these days though, why compress lossy in the first place?
Awesome! If you experiment with different resolutions and the screen doesn’t turn on again, wait 15 seconds. Without confirmation, plasma will restore the previous resolution on its own.