Sadly, in my experience, DSLinux does not work on all cards. The best card I've found for it is DSTT, which works out of the box without issues and with YSMenu you can even set Linux to autoboot.
Also, to boot the DLDI version you need a memory expansion pack. Despite what it says on their website that dslinux.nds is for the non-MEP and dslinuxm.nds is for MEP, it's kind of a lie because the latest build won't run without a MEP at all. You can get the official Nintendo DS Web Browser for like $15 on eBay and use the MEP that comes with that, that's the easiest to acquire one that is compatible.
The problem, though, is that you are using a DSi, which obviously doesn't have a slot for a MEP. While the DSi does have more RAM than an original NDS, I'm not entirely sure if DSLinux could even access it in compatibility mode. I've never actually seen evidence of anyone booting DSLinux on the DSi. The website only says it might work, so it probably doesn't.
Depending on your card, you will also have to manually patch the DLDI version with the DLDI patcher tool to get it to boot. The fact you could get it to boot at all though makes me wonder if your card is fine, because the cards I have that it is incompatible with only give a black screen and don't do anything, and it's probably just the fact you're using a DSi and not an original NDS.
With the MEP in the DS Browser it will actually give you 10 MB of usable memory. It's plenty enough memory for hobbyist stuff.
DSLinux doesn't support anything like this due to the NDS lacking an MMU, making virtual memory impossible. You are limited to the physical RAM you have and if you exceed that the system will simply crash.
