For full screen web pages, I’m using Chromium and the --kiosk and --full-screen flags in the launch command. This removes the title bar and such and just loads the web site in full screen. I only use this and the AirMouse for Netflix and PBS. Everything else works with just the remote’s arrow keys (Steam, Plex HTPC, Jellyfin, ES-DE, etc.).
I’m using this AirMouse from Gimbi. This plus AutoHotKey to remap a few buttons and the 4 programmable buttons at the bottom for TV and soundbar controls work for me pretty well. I mapped the ! button to Alt+F4, the search button to the super key, etc. The programmable buttons are TV Input, TV Select, and Soundbar Vol+ / Vol-.
I think the wallpaper was a built in one for the Cinnamon desktop, but I’ll try and find it and link it here.