that domain is not "self-custodial"... you said yourself... run your own node / domain.
not your domain = not your node...
or we get back to WoS domains?
btw... did you ever tried to install a latest web browser on an android 5?
LOL where is that security expert Tony Giorgio, recommending to run an old browser that will keep the node keys ?
You can try app.mutinywallet.com in the web browser on that phone.
you literally pointed to use Mutiny onto a domain the user can't control it. is that a lie?
Any time that domain could be shut down or even worse, you close the access. I can't name that self-custodial, even that keys are in my device.
Do you trust an Android 5 security keeping Mutiny keys?
Running his own domain, LDK node and Mutiny server for that user that barely have an old device with Android 5 is not an option. Is that also a lie?
The problem with recent apps and especially with LN is that require some more hardware and software. android 5 is really old, reduced in functionalities and power.
The only think I could think will be the old Schildbach, one of the first mobile bitcoin wallets. But that one doesn't have LN, only onchain and I think is quite obsolete, but still works.
https://wallet.schildbach.de/ so yes, you could try this one.
If you want only for "savings", then just use Sentinel. is a watch-only app. Is simple and could workd. But you will have to create the wallet and extract the xpub on another device/way, offline.
You could try Machankura, you know what they are using on those old phones.
Green will not work either, is too much required as OS level.
Custodials? Many: CoinOS, Walletano, LifePay, LNbits all on PWA but are custodials, you said you don't want custodial....
What you can do is to use CoinOS or Walletano for receiving LN.
And then swap out (they have integrated swaps) into onchain (Schildbach), when the amount is well enough.
See if you can generate segwit address in that Schildbach.
if
this is a suitable option, what could be a sweet custodial alternative? Green as suggested here?✌️