For older game systems, it's recommended you get European SCART cables for them and convert the pure RGB signal coming out it. With the exception of the original NES, all NTSC and PAL consoles up to the Dreamcast (which was VGA capable) could output RGB with the right cable. To get the best analog to HDMI conversion, you want to start with the best source of color and sync, RGB.
The XRGB MINI Framemeister is the best converter/scaler for multiple formats to HDMI. You'll just need to purchase the correct cables for your US/Japanese (NTSC) or European (PAL) systems. The My Life In Gaming YouTube channel has made individual tutorial videos for most consoles, the Framemeister, and a lesson on RGB/Sync and various video formats. Their information is helpful for any kind of device with analog output, and not just retro consoles.XRGB Mini Framemeister Review and TutorialRetro Gaming Cables
I use SCART for my SNES and Sega Saturn as they both output pure RGB which converts to HDMI beautifully. I'm speaking from first-hand knowledge. There are cheaper alternatives than the Framemeister to convert the 240P that the consoles output. They work especially well when you use 720P or 4K resolutions which 240P divides into evenly (lower latency scaling). 1080P isn't an even upscale from 240P which introduces a ton of lag on anything but a Framemeister or more expensive alternative.
EDIT: What model Laser Disc player do you have? There were some models that output RGB as well with the proper cables!
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