The only real benefit is since ubuntu is more popular, you're more likely to find getting help for it online, more readme's will have ubuntu specific install directions or packaged binaries, googling for errors and such will be easier, etc.
Very very true, I'd say that's one of the biggest reasons why Raspberry Pi and Arduino are much more popular then STM32 or other, equality or more capable at an equal or even better price, microcontroller.
How Debian feeds into downstream distros is something that Linux novices might not know, but I think that the differences aren't as intimidating as they might seem.
It's called The Universal OS for a reason, and I think if people give themselves enough credit for using Linux in the first place they would be surprised at how capable in using other distros and they can be and how much the skills transfer over.
I think part of that is because if you're used to using Windows you get a sense of learned helplessness because you're taught you're not worthy of learning how the OS works, so if the first distro people use is Ubuntu that same feeling will carry over, and you tell yourself "this is the only Linux I'm capable of using". Also when you've only ever used one distro having dozens of different options makes it seem like every one is radically different, despite having similar conventions and using the same code within distro families.
So never be afraid to "fuck around and find out" and see what else is out there, if you can use Ubuntu you're capable of using many other distros. Ubuntu is geared for enterprise deployments and cloud VMs nowadays, instead of regular people just dipping their toes into Linux like it used to be. So its status as the default user friendliest distro isn't valid anymore.
You can also get the "just works" experience from other distros, and in fact maybe more so because of all the issues with snap based applications that Canonical forces on you that add complexity, makes troubleshooting more difficult and creates a much worse overall user experience.
To my knowledge right now they are just that, concerns, no absolute proof, but why risk it when there are so many other distros where those concerns don't exist?
Also theres the whole snap controversy, yeh sadly Ubuntu's issues go beyond stability