Are you sure your drive actually works?
I’ve had to replace five optical drives in the last ~eight years as they were non-functional, but if media was inserted into them some would still spin up so part of the electronics on the drive was still functional, but they were no longer usable either in reading/writing or what I wanted them for. Most optical drives are now rather old; my failure rate is maybe extreme, but I’d just go and grab a replacement drive from a recycled pile & choose based mostly on external color of faceplate (or newest in recycle pile of those with suitable faceplate).
The machine here has no optical drive, so I went and powered up a Lubuntu 25.10 system that has an optical drive, inserted a random movie DVD & the system popped up a question asking me what I wanted to do with inserted media; I selected VLC & the disk started playing in VLC.
I sudo apt install k3b and let install, started the k3b app & it opened as expected, I tried to ‘format’ the disk & it complained the drive had non-writable media or gave me an appropriate message given the media in the drive was still the movie-DVD I’d inserted before.
If my install was Ubuntu 25.10, and I added vlc to it as I normally would; I’d expect the same result. I can’t think of a system here running [Ubuntu Desktop] 25.10 that has an optical drive though to test with (why I used a Lubuntu box; which I do consider Ubuntu anyway)
I’d be suspicious that the drive is faulty, esp. given my failure rate over the last few years, and I’d likely boot other live media (something different to the Ubuntu 25.10 you have installed) and see if you get it working there (ie. exploring if its a hardware issue, not software issue your question asserts).
I do wonder why you went for k3b or a KDE/Qt based app if using GNOME; I’d have gone for xfburn which better matches with a GNOME desktop. You could try that, but I’d actually expect the same result there (unless you’re installing the apps differently to how I’d do it etc)
If you want to explore what hardware you system sees (is the drive seen? your question implies its not and that the drive itself is working) I’d likely use
lshw -c disk
and see if it was detected. I see nothing on the box I’m replying here of optical class, but on the box I explored running Lubuntu 25.10 a DVD-RAM writer [listed] was obviously the drive that I’d inserted a random DVD movie in for my test. Sorry I can’t recall if lshw will exist on a default Ubuntu install, but it’s a tool I use myself.
Addendum: your system may have lshw as I see it on Ubuntu Desktop 25.10 media but minimal & other install options may mean not everything was installed
