Hello there and greetings from germany!
I tried to install boot9strap and sorts with this guide: 3ds.hacks.guide/installing-boot9strap-(browser)
While none of the supported websites to load the Launcher.dat worked, i used the one in the last posting here...
Can't find any threads about this particular issue on GBAtemp or the wider intarwebz. Saw one video on YouTube that seemed relevant, but it was some dude with the same issue, no solutions offered in the comments. :/