Thanks for your interest! 
UiPath 2021 has new feature ‘Custom Browser’. Your can find this properties in Open Browser, Attach Browser.
We use Chromium 66 base in-house browser.
UiPath recognize it as ‘wnd app’!! not ‘html app’ 
This make lots of problem…
So we test Open Browser activity with Custom Browser option.
But I don’t understand guide document. It says…
" The custom browser you want to use must have a chromedriver.exe executable suitable for the Chromium version on top of which the Custom browser was built in PATH"
What is it means?
Are we need to put chromedriver to specific folder? Or we need compile/build our browser again with chromedriver?
We are stuck 
Your advice will be really appreciated.
※ What we test are…
(1) Download chromedriver(support Chromium 66) and save to ‘C:\webdriver\chrome’
(2) Add environment variable path ‘C:\webdriver\chrome’
(3) Open regedit
- Add key : Software\UiPath\UiPath Platform\CustomBrowser
- Add value : Command → ‘C:\InhouseBrowser\OurBrowser.exe’
(4) Restart Windows or UiPath Robot Service
(5) Create test workflow, add Open Browser activity
- CommunicationMethod : Webdriver
- BrowserType : Custom
- URL : “http://test.com”
When we run our inhouse browser open successfully. But fail to move URL.
It freeze 10~15second and restart browser… repeat 4 times then we got fail message 
