Thank you for reaching out to us. I completely understand these questions when AIP UL client in maintenance mode.
I feel that there is a confusion around the announcement. AIP Client components include the addin, right click, viewer and PowerShell module.
While all of these remain in maintenance mode with no additional feature improvements. They are still supported and customers can and should use them based on the use cases that require them.
You can also leverage yammer for Azure information protection/Microsoft Information protection updates - https://www.yammer.com/askipteam/#/Threads/Search?search_origin=global&search=maintenance%20mode
Read all the latest MIP updates and blogs at https://aka.ms/MIPblog
Let me know if you have any further questions.