Perhaps you never noticed that another thread was created yesterday on the forum regarding xrdp and trying to get it to work properly.
While the problem is not identical to yours, it is similar enough to make me think the timing is a little more than coincidental.
Have you considered that this may be a problem with the xdrp program itself? Perhaps you need to do some in-depth searching to see if others are having this same issue with xrdp, and if a workaround/fix has been found.
Sorry I can’t be more helpful, but if the problem is not with Garuda or Xfce, then you are simply wasting your time working under the assumption that it is. The other Garuda user that reported a problem starting xrdp is a KDE user, so this would seem to indicate that the desktop in use isn’t the cause.
Good luck with your issue, but perhaps testing other remote access software is your best bet. Sorry, I can’t be much help recommending alternatives there either, as I’ve always considered remote access to be a security risk and never allow it on any computer I own.