I was entering new m3u urls for in the "TV source" area and it would not get to the keyboard. I downgraded to 2.40.2 and fixed it. I was having this problem on Fire TV 4K stick, Fire TV cube, & mibox3. I also tried the beta with no luck.

I'm guessing this is a bug.

What way for select editor? Try click on field and select "edit". Still no keyboard?

Please try last BETA version

I've tried the beta and it has the same issue. I'm surprised you are not seeing it because it has problems on 3 different devices for me. I am able to see the keyboard appear and disappear (real fast) in some instances and then I can't get it back, so I'm not able to enter any url.