I'm using Slackware-current with manually maintained [edit: actually, I wrote a python script to generate it, see other comment] grub.cfg (grub 2.06) on a MBR system, and happy I don't have GPT. Recently I tried to convert a Windows installation from MBR to GPT. What a disaster, never doing that again (but if you do need to, use gdisk [1]. It's great, I had unrelated issues). I suppose I'll eventually have to convert my Linux PC to GPT when replacing the motherboard. I haven't ever reinstalled Slackware (I just upgrade), since switching to it in 2007. Honestly there are issues with that.

Slackware just celebrated its 30 year anniversary two days ago [2] and still going strong without systemd ;) Well actually it now has eudev, which is the small unintrusive part of systemd which a lot of software these days has as a dependency. Everything is still done with rc files. Best of both worlds.

[1] http://www.rodsbooks.com/gdisk/mbr2gpt.html

[2] https://www.patreon.com/posts/thirty-years-86196804 (There's nothing on the website or announce mailing list)