Weird HTML/Browser DPI scaling issue via Windows RDP

Question

Hello!

I have been experiencing a very strange RDP display issue for some months now:

Using my HP laptop (17" 1600x900 pixels) as RDP client, remote Web-based apps are rendered zoomed/up-scaled.

• Independent of remote computer or VM (tested 3x Windows 10, 2x Server 2012, Server 2016)
• Only HTML content is affected, desktop applications and OS components render normally
• Affected are all (!) browsers (Firefox, Chrome, Edge) and Web/Electron-based apps like Teams Client, Visual Studio Code
• Only remote: local apps/browsers on the laptop work fine
• Re-Installing Win10 and even a clean install of Win11 on the laptop changed nothing
• Alternative RDP clients on Windows all behave the same
• Same faulty display with TeamViewer (!)
• If running Linux (Ubuntu) on the client laptop, RDP display is OK(!)

The laptop is a HP 17-bs0xx with Intel Core i3 and Intel HD 620 graphics.

This screenshot shows the scaled resolution in FF full-screen 1600x900 using JS and document.(inner|outer)(Width|Height):
(See attachments for the same page in Chrome and Edge)

This is not only annoying, but makes it impossible to develop web apps on a remote system via RDP.
Many apps switch from desktop to a mobile view.

This is how the Office 365 home page looks like (again, full-screen 1600x900):

Findings and conclusions I have so far:

• I found nothing on the net describing the exact same behavior (HTML-only up-scaling with all engines)
• It's a client issue - only one laptop used as client is concerned, all other machines interconnect fine
• It's a Windows (10+11) issue - a Linux RDP client works just fine
• Setting the resolution manually in the RDP client doesn't help

In the RDP session to a VM, WMI reports the resolution correctly:

I'm really looking forward to any help you can give!

Markus