Heck. I found a couple old R4 cards. ... Ones really really old, the other is newer and is meant to work on 3dses but... I think it's defunct because the site (apparently a newer site) doesn't seem to list this R4 card any more... So it might basically be dead, and it doesn't work on my dslite now either.
maple classic™ 
@Nine what happens? does it get stuck on "loading"? might need kernel files in the microsd, they won't boot without those
mine once had to had its firmware reflashed to keep working on a 3ds, and that could only be done through a regular ds
@squirrel Yeah, tried out the other firmware and it works fine on my dslite but I guess it's blocked by the New 3ds XL's new firmware. welp. ^^;
@Nine oh, so it's not bricked on regular DSes? you should be able to make it work.. my 3ds is (i think) up to date (though it is rooted) and my flashcart still works with it (still worked before the root)
it did the "an error occurred" after a 3ds update but a firmware update on the flashcart worked
the firmware update isn't just replacing the kernel files, it's running an .nds app on a ds where it can run, to actively flash the firmware inside the cart (not the microsd)
@squirrel Yeah, I'm not entirely sure how to get that working on this one, it doesn't seem to have that option for whatever reason.
Theres an Upgrade button but...it does nothing once I tap it.
@Nine can you get any info on which r4 model it is? what does the sticker say?
@Nine I think your flashcart is way newer than mine... so following the instructions in that website don't do anything?
Urrghhh I wish I could be there to be of more hands-on help
@squirrel Yeah, I can click the Updateb utton on my dslite, but there's no other options, as if it's already on the most current firmware?... googling gives me nothing :/
apparently R4 carts are rife with problems like this, and the update proceedure is not clear.
This is compounded by just how difficult these flashcarts are to get in the UK D:
@Nine yeahhhhhhh there's uh
SEVERAL versions and clones
mine doesn't even have an update menu like this at all, I had to run an nds update program separately
@Nine I wish someone had taken better care of like, archiving and categorizing cart IDs and such so it'd be easier to find firmwares but believe it or not i guess there just wasn't enough demand
@Nine this might help? especially the link of "mega list of r4 clones" in it
@Nine looking through this http://leafmoon.users.sourceforge.net/xenonnds/pukiwiki/index.php?FlashcartClassification
looks like it could be either an Acekard2 or DSTT clone, which might help narrow down what kinda firmwares it can fun
@Nine anyway i gotta go to bed ... like 8 hours ago, so i hope this helps!!! ;;
@squirrel sleep good! <3
@squirrel Yeaah looks like I got a DSTT clone one D:
@squirrel It's an R4i-3ds . It's not got the v1.4.5 or RTS sticker on it, and the web address points to http://r4i-sdhc.com rather than a more recent site. (ironically the firmware on that site doesn't work, but the one on the more recent site does?)