Standalone office 2019 and Office 365

Our office is currently using standalone installs of mostly Office 2019 and some Office 2021. I understand the support will end this year for them but will they still work with Exchange online if we go with Microsoft 365 Business Basic subscription? We only have 30 or so users and cannot justify the cost of moving everyone to the next step up. I work for a small government agency and all costs are very scrutinized. I anticipate we could in the next couple years, but not before the October deadline. Will the older office clients get blocked like happened to Office 2013 and 2016?