It is fine to use Discourse, what issue do you see preventing you to do so?

Sorry should have been more clear. There is no tag, but it seems I am now able to create one.

I find "l10n" pretty confusion, but should #l10n-team or #localisation-team be used?

Edit: well okay the issue was in the title XD

Localization is a really complex term, most people won't know it (l10n is same)
Using "languages" or "translation" would make it easier to understand by non contributors.

It really depends how it is used, whatever happen, it is fine to use whatever tag you feel comfortable with.
Usage is the most important, it will decide how it goes over time.
And this is the right way to go, simply invite contributors/users to do so and see how it goes.

Just reopening to give my thought to this and then closing again. ;)

I think in this moment there is no need to create a tag for our team. Normally our communication channel are rather quiet. Of course, it can change in the future and we can reconsider this.

Instead, we can use existing, no team specific tag(s) for the Fedora Discussion (as jibecfed suggests). We can even ask to make alias(es) for some, like "translation" <- "localisation". And we might set the tag(s) in discourse as "watch(ing)".