Yeah, the above dump was from the Brother p-Touch software.
I have both Brother p-Touch label printers and a Zebra label printer. The software for the former runs on Windows/MacOS, whereas the latter is only Windows.
The Brother really needs dedicated software that understands its features and media sizes.
Fortunately the Zebra can also behave like a normal printer, which is great for printing things like shipping labels. But a lot of the time I actually do still want traditional label-design software to use with it, for all the features that provides.
I'm not aware of any good way to do this, for either printer, from Linux. The best you ever find is someone failing to understand the problem, detailing cryptic ways of configuring CUPS that don't actually work 75% of the time. But there's still nothing out there for actually designing the labels. No, a word processor template doesn't count. Neither does some half-built unmaintained project like gLabels.