I'm using OpenWrt 19.07.3 on TP-Link Archer C7v2/5 routers. If I login to the units via IP -> Login Page -> Enter user/pass -> Submit the login succeeds and I land on the status page.
I've tried to bookmark the "http://IP/cgi-bin/luci/admin/network/wireless" page to land directly there after login. If I'm logged out and navigate to the URL, the login page is shown. After entering user/pass and pressing "Submit" to login, OpenWrt LUCI redirects me (correctly) to http://IP/cgi-bin/luci/admin/network/wireless but shows an error. I'd expect the wireless page to show instead.
It works with current Chrome. I'm using remote desktop manager (from devolutions) to login and store credentials. RDM makes use of a chrome wrapper (EssentialObjects Browser), probably limiting session cookies. It always works with the tool if entering the web page through the root "/". Entering a full address to start a new session leads to the above mentioned error, reproducibly.
Only the IP was hidden in the above screenshot. You're right, it's strange but the ticket should go to the EO web browser support (product used in rdm) and say "what are they doing about wrapping chrome that breaks the site's redirect after login".