Yes, I modified the source code for a very small utility that needed a newline, and I recompiled it. It was truly trivial but I did it.

kernel, LFS, some personal code, but nothing recent

although I sometimes have to chase down library dependencies.
linuxfromscratch has been my distribution over the past many years
although it has become tiresome lately.

I really like to dabble in compiling open source projects for my own use.
I recently discovered the Urho3D game engine, its really great.

I've compiled a few things in the past when they weren't available or the distro's version was buggy, but that was in my Fedora days. The biggest program was Fontforge. One thing I learnt was that anything that doesn't use the standard automake system is likely to be a problem!

many times over the years

Numerous times over many years, first on Solaris and then on Linux.

Now, I typically run Ubuntu LTS servers, and I try to stick with the managed apt packages. These get security patches, which I apply regularly. That's much easier than tracking every application you built yourself for security updates and then applying them yourself individually across multiple servers. Of course, this is a system administrator's perspective, not a developer's perspective.

That said, there are applications that I routinely build from source. One is Amanda. I need features that are not in the managed package for Ubuntu, and I want to control the options. There are also applications that may be important for our environment that simply aren't available through Ubuntu; for example, Galaxy (computational biology or bioinformatics software).

Hmm. Then there's the ancient times, compiling source on a Honeywell G635 mainframe. But, I think that was in the days before opensource was a thing. We did share code sometimes, but there was no internet and nothing that you would think of as a repository.

Had to compile cdrtools to get them installed and working a couple of years ago when k3b was defaulting to use other burn apps that failed to support burning to blu-ray discs well enough to be reliable.

Also smake, and I don't remember why now, but it's probably because I needed it to run the make scripts to build cdrtools.

Yes, I had to compile xawtv to get it to work on Slackware. Was a little difficult, because
I had to hunt down some other libraries etc. to fill dependencies. Little frustrating but
really valuable training. Haven't had to recently since I switched to MX Linux a few years
ago (yay team!).

Many times I have compiled source, for several reasons. Often to try to ensure what I was making fit my system and needs.

I have never even seen a source code let a lone compile one since that's way out of my area. My hard drive in my head is filled to capacity with a vast abundance of other knowledge.

Emacs, TeX, misc stuff not included in Slackware and of course the software I've written for myself.

I added support for a device to Linux by adding a USB id. I sent a patch via the mailing list so the code is now in the kernel. I also made multiple fixes to Chocolate-Doom.

Not an application but I've compiled the kernel (in a Debian way) a few times for fun and to get things working.
I've definately compiled something else but the program escapes me. I do so so very rarely but, on occasion, it's the best way to get things working.

Everything from time to time. Last I cross-compiled the gcc suite (ct-ng is my friend).
Emacs for different platforms. I can't live without it.
Many more than I can remember.