Yury Zaletsky explains how to turn on the new UI in 2023R1
Of course you can only do this when you run Acumatica ERP on your own server that gives you access to the web.config file .
If you own AWS, then you will need to modify web.config . If on Acumatica AWS, then you will need to create support case for web.config file modification. Also I strongly not recommend such tests on production instances