This has been bugging me for a while. Out of the box, I configured my Librem 5 to use the 5 GHz band - but the signal range was not very good e.g. no signal where I had my charger, which was a pain. I could have put in a second WAP but …
Spurred on by your post, I changed my Librem 5 to use the 2.4 GHz band instead. Not only can I now get signal where I have my charger but it looks like time-on-battery has increased too. Not dramatically but enough to be helpful.