You can go 'Spectate' if you dont want your tee to spawn, then 'Join Game' otherwise. Press ESC and you will see the options on the left.
If you want to change your tee to something less obvious, you would need to scroll through the skin list.(edited)
its not that hard, just download ddnet map db and set sv_test_cmds 1 in autoexec.cfg
23:48
then you can put the rcon password to smth like "test" and anyone can join and use rcon commands, but ddnet doesn't host them myself and the servers i hosted didn't get too much players