As a general rule, you can expect that released versions of Ubuntu flavors will not get newer versions of included software. In other words, if you have 4.3, you’re not going to get any higher.
Don’t know what to tell you. Lubuntu is not responsible for maintaining OpenGL. That would be the job of Ubuntu maintainers. You can certainly contact them about the state of packages in the Ubuntu archives in general. I have serious doubts that you are going to be able to convince them to make such a big change to any package, though.
When a version of Ubuntu (and its flavors, including Lubuntu) is released, there is a set version for all the packages contained in the archive for that release version. In a very rare case (there’s actually a very restrictive process one needs to go through to make an exception) versions will increase. Those exceptions are almost always bug fixes (i.e. small patches) and not major or minor version changes in the upstream software.
Let’s consider this within the context of Lubuntu: our long term release version right now is Focal/20.04 which has LXQT 0.14. Even though LXQt 0.15 is in Groovy/20.10 (and what will be Hirsute/21.04 should have 0.16) and is much improved over its predecessor, we have no plans on increasing the version of LXQt within.
If you expect to have the latest software all the time, you should consider a rolling release distribution or compile and/or package everything yourself. That’s just not how many, if not most, Linux distros work.