[Interest] Qt 5.15 LTS vs Qt 6.2 LTS

[Ulf Hermann]

Long story short: You can have a Qt 5.15 LTS. You just have to pay for 
it. You can even have Qt supported on obscure outdated platforms, as 
Volker mentioned. It's just even more expensive. The price is high 
because there is a lot work involved in making this happen and the 
number of customers requesting it is small.

There are other toolkits for which the cost of such maintenance is 
lower, mainly because they didn't evolve so much since the days when XP 
was the latest and greatest. Some toolkits are even written from scratch 
with mainly backwards compatibility in mind. You will understand that 
there is a trade off involved here. If you want to be compatible with 
everything in the world, you can't add many new features.

> 1) On rare occasions patient killing bugs like this one get fixed.
> 
> https://bugreports.qt.io/browse/QTBUG-12055 
> <https://bugreports.qt.io/browse/QTBUG-12055>
> 
> This has very little to do with "security" unless one puts application 
> stability under the security heading.

That's exactly the safety (not security) argument I was expecting. The 
patient killing bugs in the underlying OS and drivers etc will not be 
fixed anymore, though. So even if we had decided to support XP with Qt6, 
you still wouldn't have gained much.

> 2) Updated hardware support.

I wouldn't trust a hacked together system with 3rdparty drivers and 
outdated software monkey-patched to work with my shiny 4k monitor to be 
free of patient killing bugs. Or, I would only trust it if all that 
stuff is carefully tested to be compatible with each other. Such testing 
and bug fixing is expensive. Here we're back at square 1.

best regards,
Ulf