I had partial results. Host page is launched in Chrome on a Dell Desktop, client version: 
23.9.8.8811

Worked = normal usage of session screen
FAILS = A screen is visable.  But only way to update any dialog boxes (like Windows Explorer or any other box) is to use Toolbar, Cntrl-Alt-Del and then press Cancel

Tested this with 
DELL OptiPlex 3020M Micro - Intel HD 4600 integrated.  Worked

DELL 3630 Precision with Nvidia GTX 1080 - FAILS
DELL 3630 Precision with Radeon RX 460 - FAILS 

Confirmed. 

On remote machine, client version: 19.2.24707.7131

Motherboard: GA-970A-DS3P FX

Monitor: Samsung T213

Video Card: Nvidia NVS 310

Nvidia driver 392.56 (downloaded 8/16/2019)

Resolution, 1600x900

Get blank screen as soon as monitors are unplugged from video card, resolution goes to some 4:3  resolution

Monitor using DisplayPort to DVI-D cable/adapter.

Observed, upon rebooting, briefly get the "restarting" page

On the host page, the preview of the screen does update. 

Connected monitor cable to video card, image comes back to normal.  

Turning off monitor, not affected.  

Pulling power cable from monitor - not affected

Removing the DVI cable from the DP adapter (leaving DP adapter connected to video card) - affected, screen goes blank but does not change shape.

On the Host Access page, there currently is no way (under the default theme w/o any skin extension installed) to change the widths of the columns.

Under Administration page, Appearance...

Visual Theme

It would be helpful to have a toggle of "standard" or "flexible" column widths

Currently, there is an extension for this - it's version 1.0, (has been updated by t2service Modified 7/9/2017)

NOTE: But it does NOT work with build ScreenConnect_6.3.13446.6374_Release (as of 09/14/2017)