There is a good solution: https://www.cybelesoft.com/thinfinity/remote-desktop/server/ We use in our company for some cases where RDP use is prohibited. Works fast and not expensive at all. I hope it helps.
I’ve used several solutions.
This app is awesome, I’ve used it for years: https://www.cybelesoft.com/thinfinity/remote-desktop/server/features/remoteapp/
and it’s FREE https://www.cybelesoft.com/thinfinity/remote-desktop/workstation/free-license/
Another approach is to use OpenVPN. This will work behind any router/firewall. I also run OpenVPN on my Synology NAS and connect via an IOS or Windows client.
It’s very possible to use a VPN router or device on the inside of any ISP router; personally I use openVPN on my Synology NAS.
A very awesome remote product is Cybele Thinfinity that allows HTML5 remote control of RDP devices. Thus via HTTPS you can remote control any Windows device with any HTML5 compliant browser (no plug in or app). And it’s free for one client.
https://www.cybelesoft.com/thinfinity/remote-desktop/server/features/remoteapp/
Proper RDS gateway, Citrix, (and) (or) https://www.cybelesoft.com/thinfinity/remote-desktop/server/ to RDS or workstations. (HTML5 is a godsend!)
RDS gateway to workstations is fine.
^ ALL OF THESE ARE DUO 2F PROTECTED
VPN's - we use them for admin. Very few users have access to a VPN and if they do it's very tightly regulated. Most implementations of a VPN forget the N and just dig a big fat hole into their network. We restrict ports to bespoke apps mostly and use thin tech for all real access.
There have been a few outsiders who have genuine direct file access (for reasons), but.. the risk is so very high we tend to try our damn hardest to find a safer way.
Depending on your legacy apps and needs you may want to check out Thinfinity Remote Desktop Server. You can run RDP session in any html5 browser (Similar to RDWeb html5, which is a little clunky or Apache Guacamole). Its pretty inexpensive and very easy to setup.
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https://www.cybelesoft.com/thinfinity/remote-desktop/server/
Thinfinity Remote Desktop was released back in 2010. It was the first HTML5 RDP client. At that time, the HTML5 was so basic that did not support remote sound!
HTML5 and Thinfinity evolved with the years and now the remote desktop client supports remote audio, remote printing, FTP, regular RDP, screen sharing (VNC-like) and the Workstation even includes a presentation mode for up to 16 participants.
For Linux users, the Server edition is compatible with with XRDP Server.
If you need a web RDP client for home (free) or corporate use (paid), you should take a look at it.