True. However, if you want to use the npub.cash address that starts with your Nostr npub (of course you would), you'd have to share your Nostr nsec - which cashu.me acknowledges is "dangerous and not recommended".
Discussion
I should adjust that, it's a bit of an exaggeration. I use it that way. you can also use a signing extension if you want though.
Yeah... the signing extension via cashu.me works great on desktop. I don't believe it's available for mobile, though (at least not iOS anyway).
It think "dangerous and not recommended" could be an exaggeration - but I think that depends on how secure you wish to keep your nsec. Personally, at this time, I consider my nsec/npub disposable, but I still try to practice good nsec hygiene by sharing it no more than is absolutely necessary.
you can use the built-in wallet nsec (or another throwaway one) and purchase a username for it on npub.cash
It hadn't occurred to me to pair a custom address with a throwaway nsec. That's a great idea! I'll definitely keep that in mind.
On iOS you can use the Safari extension Nostash by nostr:nprofile1qqszw70nm86zcl0wzlcwd0xulzdgl82e95v78vdm6fl0rnlarfle35gpzamhxue69uhhyetvv9ujuurjd9kkzmpwdejhgtcpz4mhxue69uhhyetvv9ujuerpd46hxtnfduhszythwden5te0dehhxarj9emkjmn99u3huzze.