fTelnet (https://www.ftelnet.ca) is a browser-based terminal client.  The author just released some changes I submitted and it's working great for me on my BBS atari.electric-estates.com if you want to see it. BBS is a work in progress but shows off the beautiful Atari characters in the browser!   For BBS Sysops, use  the wizard on the site and select Atari emulation.  If your  changing you current config to its just   Options.Emulation = 'Atari';