It is currently still fully supported with iPadOS 15.5. That is the most current iPadOS version available for any iPad.
It should not lag or feel noticeably slower than it does right now with iPadOS 15.5. Its not a major update, so should not change much in terms of performance.
Details here: link-> About the security content of iOS 15.5 and iPadOS 15.5 - Apple Support
It will not be supported with iPadOS 16 in the fall however.
It is a good time to consider saving up some money for a newer iPad. You should still have around 1 or 2 more years of app support, even if no more iPadOS updates are available for it.