I have the detailed instructions that I carried out (including building uuu from source, back then!) and a log from doing the actual firmware upgrade but one thing that I don’t have is a reason why I updated that firmware e.g. I don’t have a link to a forum post that might elaborate (and I certainly don’t remember as it was 5 years ago).
I guess you would have benefited from those instructions but you managed to get there successfully before I booted for the day.
tps65982-librem5-dp-alt-mode.bin is proprietary, closed-source binary firmware (a “blob”) used for the Texas Instruments TPS65982 USB Type-C and Power Delivery (PD) controller.
As such, I believe that Purism is trying to maintain that it does not intend to have users update that firmware once the device is delivered to the user.
That file contains two parts - the proprietary blob from TI and configuration register sets which come from project files authored by Purism also present in that repository. This “update” is about these register sets.
It happened to me recently too. What worked was, booting Jumpdrive and then rebooting.
Connect one side of the cable to laptop, press volume up button when inserting the cable, check if it is detected using lsusb (it should list a device with NXP), then boot jumpdrive, this showed and error but next boot was fine.