You can use VNC to make an android tablet into a 2nd monitor. The latency isnt good enough for playing games or anything but for web pages and documents it works great.
I've recently been using a piece of software called RustDesk, which so far feels pretty performant, better than VNC, RDP, TeamViewer, RealVNC etc.: https://rustdesk.com/
You can host a relay inside of a Docker container if you need it as well and it even supports AV1. There's also password auth for each device and permission control.
They have a mobile app too, though I haven't used it as much as the desktop variety, might be worth a shot.
Been using kagi for awhile, also in Portugal. Google shopping is the one thing that Kagi can't beat them at yet. If i'm looking to buy a product online not from amazon it's still the best option.
Man what? I always use AMD with zero issues (arch). AMD is known as the best graphics card for linux. Your experience does not match up with what is typical.