Is it possible to check rdp connection from browser?

The easiest option is to check if the RDP port can be accessed using telnet. Default RDP port is 3389 the example may have to be changed according to the configured RDP port.

Open a command prompt Type in "telnet " and press enter. For example, we would type “telnet 192.168.8.1 3389” If a blank screen appears then the port is open, and the test is successful. If you receive a connecting... message or an error message then something is blocking that port. It could be the Windows firewall, a third party firewall like Norton's or a hardware firewall between the PCs. What a successful test will tell you:

If you can both ping and telnet to the other computer, this shows that there is a network connection and the port is open between the two computers.

https://www.opcsupport.com/s/article/How-do-I-ping-and-telnet-to-test-a-tunneller-connection

If you are trying to test from a browser chrom has an option which could help your question. Please refer: https://www.accuwebhosting.com/blog/how-to-connect-remote-desktop-using-a-web-based-interface/