Broadly, I want to highlight that while some of the comments here have focused on "why not just run a full node on your RPi at home", that's simply not realistic for normies. Unless we want ~everyone to be stuck using custodial providers, things like Mutiny are absolutely critical to getting people onto Bitcoin/Lightning. Mutiny is still super new, and there's been some hiccups, but the rate they've been shipping has been impressive and they've definitely fixed a boatload of issues over the past month or two.

I want to respond a bit to this, because this implies that there's some general node compatibility issues here, but that's not really the case. These days we don't really see any issues between LDK and CLN or LDK and LND regarding general compatibility issues.

Mutiny has suffered from several force-close issues, sadly, but I understand they've made good progress on several of them (including contributing upstream to LDK the API tweaks they required to have the flexibility they needed for their improvements!)

a) Until recently LDK did not fully support anchor channels, CLN, which Mutiny's LSP currently uses, only supports anchor channels as a development feature, and Mutiny has not yet had the bandwidth to integrate anchor channels. Without anchor channels, lightning nodes to have to enforce the feerates on the channel as within a range that their feerate estimator gives them, as otherwise the channel is not enforceable on-chain. LDK is relatively strict about this, other lightning nodes have loosened their enforcement here to avoid force-closes and instead risk on-chain enforcement can fail. Of course anchor channels addresses this, but in the mean time Mutiny has contributed upstream to LDK to give more flexibility to users to let them loosen the enforcement, which I understand Mutiny now has.

b) Mutiny doesn't generally have the users' private key online, and many users receive HTLCs which are set to expire soon and then they close the site and don't reopen it for a week. Sadly, at this point on startup the channel has timed out and we have an HTLC which the lightning protocol mandates we go to chain to enforce. We've chatted a bit with Mutiny about how we might go about working around the Lightning protocol's requirements, and I'm quite confident we'll figure things out, with better initial sync steps in LDK and Mutiny, and looking towards the future with things like async payments.

c) Mutiny has been taking advantage of a beta feature in LDK where storage is asynchronous, as well as built a lot of infrastructure around supporting the same wallet/node running on several different machines at the same time. This is an impressive bit of engineering, but still has some kinks we're working out.