No supported JavaScript runtime could be found.

[githottub]

From output of file that won't d/l due to error:
WARNING: [youtube] No supported JavaScript runtime could be found. Only deno is enabled by default; to use another runtime add --js-runtimes RUNTIME[:PATH] to your command/config. YouTube extraction without a JS runtime has been deprecated, and some formats may be missing. See https://github.com/yt-dlp/yt-dlp/wiki/EJS for details on installing one

Note: Using the latest version of yt-dlp. Have never seen the error above previously.

***** UPDATE with SOLUTION*****
Due to recent anti-downloading steps taken by Youtube, the old javascript engine used by YT-DLP was no longer able to cope with the issue. Therefore, they have switched to deno.exe which is much more advanced and also able to be used as a portable executable not requiring installation = YT-DLP will simply look for it in the same folder and use it if there. So, I solved my problem by downloading it from https://github.com/denoland/deno/releases where there are versions for different operating systems. Just get the one you need and unzip into the same folder you have for yt-dlp and ytdlp-interface.exe

Hopefully @ErrorFlynn will start including deno.exe with YTDLP-Interface and add an update feature in settings as currently exists for yt-dlp and ffmpeg.

[ErrorFlynn]

Deno has been bundled with ytdlp-interface ever since it's been supported by yt-dlp (or alternatively QuickJS for Win7 or 32-bit, check out the release notes for v2.17.0).

I'm guessing you've had Only extract ytdlp-interface.exe from the downloaded archive checked, so deno.exe didn't get extracted when updating. I don't know if I'll add an update feature for deno and QuickJS, it seems problematic but I'll consider it.

[githottub]

Deno has been bundled with ytdlp-interface ever since it's been supported by yt-dlp (or alternatively QuickJS for Win7 or 32-bit, check out the release notes for v2.17.0).

I'm guessing you've had Only extract ytdlp-interface.exe from the downloaded archive checked, so deno.exe didn't get extracted when updating. I don't know if I'll add an update feature for deno and QuickJS, it seems problematic but I'll consider it.

It is checked; however, I don't remember ever checking it and, indeed, didn't even know what effect that setting might have until you just explained it. Is there any way it could have been checked by default? Otherwise, maybe it somehow got clicked by accident.

In any case, just to clarify, if that setting is unchecked will deno.exe automatically get updated whenever ytdlp-interface itself updates?

[ErrorFlynn]

Is there any way it could have been checked by default?

Yes, it's checked by default.

In any case, just to clarify, if that setting is unchecked will deno.exe automatically get updated whenever ytdlp-interface itself updates?

Possibly. It will get overwritten by the version bundled with ytdlp-interface, which will be the latest at the time I release the new version, but not necessarily at the time you update the program.