Incubator is using Vector 2022 as the default skin, but that is not currently compatible with sign language wikis (reported at T312844).
The default skin for these should be switched back to Vector until that is resolved. If it's not possible to change the default skin for individual wikis, then Incubator itself should be switched back to Vector until Vector 2022 is usable for all of its wikis.
I don't think this is practical, as many projects on incubator do not have this problem and need Vector 2022 skin as the default.
I've disabled the gadget on Vector 2022 skin for incubator in the mean time:
https://incubator.wikimedia.org/w/index.php?title=MediaWiki%3AGadgets-definition&type=revision&diff=5493805&oldid=5431088
Which projects need Vector 2022 for basic functionality?
I've disabled the gadget on Vector 2022 skin for incubator in the mean time:
https://incubator.wikimedia.org/w/index.php?title=MediaWiki%3AGadgets-definition&type=revision&diff=5493805&oldid=5431088
You've broken it completely. That gadget is necessary for SignWriting wikis to work at all.
I disabled the gadget. I can also restore the gadget in it's broken form if that's preferred? My understanding with incubator is that it's a shared resource and most new projects want the same default skin as MediaWiki.org.
On long term, I'd be more than happy to help get this working again but I'm unfamiliar with the code. Who maintains the gadget?
I saw T312844#8133920 just after posting this so let's continue the conversation there.