Can you connect e.g. from Windows to Linux and vice versa? Or from Android to Linux? I believe, KDEConnect was specifically designed to address this (https://kdeconnect.kde.org/), have you had a chance to give it a try?
1.) Enable RDP connections to Wayland sessions, whether they are already running locally, or not (i.e., start a new session if none exist when logging in remotely)
2.) Set that up via SSH, for a remote machine that has no display and anyway is remote so you cannot physically log into it (still very fiddly, but possible)
My requirement is just that every system be remotely accessible via both GUI and CLI. So, RDP (or, theoretically, VNC over SSH would be OK) and SSH.
In the old X11 days, all major Linux distributions met this bar. XRDP worked most everywhere. But Wayland is a very different story.
The only Linux distribution that has Remote Desktop working on Wayland is Ubuttnu 25.04 ("working" per the above, not some "log into the GUI first locally, and then share your desktop" — that almost works in KDE but the experience is very buggy).
The previous editions of Ubuttnu with GNOME almost worked, but logging in remotely would kill any GUI sessions already running locally.
I can still achieve this using X11, so I do. But that doesn't work for my own personal workstation, because I have too many modern (4K or better) monitors for X11 to reliably work. So I need Wayland to drive my actual, physical monitors — and therefore am stuck with GNOME, because I really do need occasional remote access to the entire machine.
I connected to RDP sessions from Linux, macOS, and Windows. (And actually, iPadOS — using Microsoft's app which used to be named "Remote Desktop" but then they bizarrely renamed it "Windows" — leaving me in the rather ludicrous position of saying "I make a remote desktop connection from my Apple iPad to my Arch Linux workstation, using Windows from Microsoft..." ¯\\_(ಠ_ಠ)_//¯