We have a few T30s in our organization. Can we do a short-term subscription renewal since the T30 is EoL on June 2023?
You can apply a one year subscription to each of them, but it will cut off at June 2023.
If your devices were cut off on Dec 31 due to the previous end of life on these devices from a subscription that would have otherwise continued contact customer care (using the support center button at the top right of the page) to create a case and have them adjust it to one year from its start date up to the end of June (if it'd been renewed in June this year, for example.)
WatchGuard Customer Support