We have a web app developed in Flutter which runs totally fine on Chrome/Firefox/Edge on any normal computer or smartphone. When we tried it on a brand new LG TV (not sure about the model, but one that is supposed to be an expensive professional model meant for 24/7 operation), it seems to load incredibly slow. I believe the "flavour" of webOS on this TV is called "signage", and it also says webOS 6.0. We're using the same WiFi on the TV as on computers/smartphones, and other webpages (google.com for example) load normally (well, at least not extremely slow, but noticeably slower than on a computer).
When going to "Play via URL", entering the URL and hitting "Preview", the screen goes white for ~1 minute, and then the app appears. Once the app has loaded, it is not terribly slow but it has some weird rendering issues, where it kind of seems to render a new frame and then an old frame again and then the new frame again, especially for text that changes frequently (like a digital clock which displays seconds, but other UI texts as well).
Same result after restarting the TV and letting it open the URL automatically on startup (i.e. not using preview mode).
When testing on a computer with the WebOS simulator with WebOS 6.0, the app works just fine. But the user interface on the simulator is very different from the "signage" version on the TV - on the simulator we had to create some kind of webOS app (which basically seems so just be a shortcut to open the browser on a given URL). Not sure if there is a way to install the same kind of shortcut app on the TV, at least we haven't found such an option yet.
Any ideas? Is the browser in webOS Chromium-based?