OK so most of the info on using the HA Learn Command feature indicates (to me) that it’s an iterative process of defining a command to learn then pressing the remote button, saving the code and repeating.
I found this vid that shows how to batch learn. Basically define every button you want to learn on a specific remote, then step through pressing each one in turn, prompted by HA. That seems much nicer than the impression I had.
And to guess an answer to my own question about Broadlink Manager, I guess I would have had to install Docker first then pull the image? Or something, I know jack shit about Docker.
But I see numerous comments along the lines of: it took so long to get Docker and BL Manager set up and working that it would have been quicker and easier to just learn the codes in HA.
That’ll do me.