Just to confirm it, I have the same problem that other users are reporting: I load the emulator in .cia, the menu appears and when I select a rom, the console stays frozen forever and I have to force shutdown with the power button.
In my case I have a New3ds Xl console with double ips screen, a 32gb gskills sd card with a 32kb cluster. By my own decision, I have the console outdated in a firm 11.5 and with luma3ds "pre-rosalina", 7.0.5, to avoid arm11 exceptions and other problems with some older homebrew, like the Eduke3D .cia version which is also a port of Masterfeizz. However, I haven't had any issues with the newer homebrew so far, like Xash3d and ioquake3 (also from Masterfeizz), and also the most current versions of retroarch.
Perhaps it is due to the version of ctrulib that Masterfeizz has used to port this emulator, if it is a recent version it may be a possibility that there are compatibility problems with old cfw, at least in my case it would be a plausible option ... However, If what other users are saying is accurate, they say they have a 100% updated console and the error persists.
In any case, thanks Masterfeizz, thanks to your work and the work of a few who have ever developed game ports and emulators for 3ds (elhobbs, rinnegatamante, Mr. Huu, bubble2k16, nop90, aliaspider, justinweiss, jgdleaver and other retroarch folks ... Sorry if I leave any), currently we have in this console a great variety and quality of homebrew, comparable in results to some of the most active scenes of the past.