Screenshot of QEMU VM showing an ASCII Gentoo Logo + system info
I followed Mental Outlaw's 2019 guide and followed the official handbook to get up-to-date instructions and tailored instructions for my system, the process took about 4 hours however I did go out for a nice walk while my kernel was compiling. Overall I enjoyed the process and learnt a lot about the Linux kernel while doing it.
I'm planning on installing it to my hardware soon, this was to get a feel for the process in a non-destructive way.
Oh, I missed this response, sorry!
The example in question there is freeciv, which supports each of those frontends. Typically you're going to pick the one that your DE uses, but because I maintain the package I had to go through and test it all when I updated it and converted it to the meson build recently. :)
https://github.com/gentoo/gentoo/blob/master/games-strategy/freeciv/freeciv-3.1.0_beta2.ebuild#L106-L140 should give you some indication of the complexity that I had to handle here. Not every app supports every toolkit, and this supports more than most!
Edit:
All that complexity means that if I set, for example,
USE='sdl qt6'the build will produce a client for each of those toolkits. Most users don't have to worry because at least one will be inherited from their profile!