Netbird and RDP? The free tier for Netbird allows a few users and I think 5 clients. If you want to host it, you can host and run this locally on your own servers or out on a VPS/colocation server. I should mention that OPNsense has a Netbird client built in, so if you happen to have an OPNsense on the far end, it works pretty well, RDP and a http(s). I've had mixed luck with sending files, that might be my LTE internet service though, I can get about half way when transferring things like ISOs to my lab, then it drops. Pretty sure the LTE/5g connection gets mad, wish I could get fiber and 200/200 service (or better), our cable system is garbage here, hasn't been updated in over 20 years and the amps are showing their age.