Maybe WinCDEmu?

Thanks, I tried that already. Just mounts the data part.

I figure I should just run in software mode where this is not an issue.
After correcting game.cue and gamed.cue (https://community.pcgamingwiki.com/files/file/744-fixed-gamecue-sheets-for-quake-the-offering-gogcom-version), there was the performance issue for resolutions above the initial default. Only changed the "cycles" entry in [cpu] to "cycles=max" in dosbox_quake.conf.
Running 800x600 with Trent Reznor soundtrack and no issues!

I take it you also tried the program mentioned in alooper21's response as well then? I only ask because it would be beneficial to others with the problem in the future if you mention what didn't work for you so they don't waste their time. Hopefully someone finds software that isn't junk and can accomplish the task eventually.

Actually, I haven't tried UltraISO because it's paid. I only used free software.

By the way, I tried CueTools to extract the audio tracks from the image provided by GOG but couldn't make it work yet. If I do, I'll probably start a new thread with the procedure.

Understandable. I wasn't quite certain if you'd tried all that were previously mentioned in the thread and found them either incapable of accomplishing what needs to be done or loaded up with crap like cryptominers or not.

I might be a tad late to the party but for ripping virtual CDs like Quake's with audio tracks, I use bchunk. Originally developed for Unix/Linux, there's a Windows port: https://github.com/extramaster/bchunk/releases

It gives the audio tracks as .wav files, and then I use my favorite encoder for ogg/flac/<whatever>. I find this method helps me avoid shady tools that install adware or bitcoin miners.

Thank you for the advice. Just used bchunk to extract the WAV and fre:ac (open source) to convert to OGG and it's working flawlessly with Quakespasm.