Most of the SCART to HDMI converters you find on Amazon and the like are designed for video, not videogames, and don't even handle the Saturn's 240p signal correctly. You get a ton of input lag and artefacts in the image.
Luckily there ARE scalers designed for old consoles. Compared to a few years ago there are now some excellent choices, there are several I could recommend here...
Budget end - RetroTINK SCART - Great results plug and play.
Mid range - OSSC Classic - Excellent results on most games, a few titles with specific screen resolution changes like Die Hard Arcade are still problematic
Higher end - RetroTINK 5x - Next generation scaler/processor that scales as well or better than OSSC Classic and handles difficult games like the aforementioned Die Hard Arcade.
Deluxe - OSSC Pro - Still in development but will have every scaling feature you could dream of and then some.
The first two are available on my store, the 5x has only just come out and I've not been able to get stock as of yet. The OSSC Pro is still in development. I won't link in case people think I'm spamming but it's in my signature.
Also, you will need to make sure you have a fully wired RGB SCART cable, a SCART cable that just carries composite video won't do, so make sure you buy a SCART cable from a reputable reseller.