Seems that many read/writes on a microSD card would surely kill it pretty quick...?

To try it? Maybe To use it? Too much hassle for nothing. You will not gonna use onchain wallets on your mobile, only LN. And for a LN node you don't need a full blockchain on your device.

Nowadays you can spin up a full bitcoin node on any dumb PC. From that home node you can connect any other mobile app to sync, using Electrum SPV, Neutrino or directly RPC. Many mobile apps can do that now.

I haven't got to the running a node part yet as I'm waiting on a power-and-charge adapter/splitter doodad so I can plug it into charge and a USB3 SSD, but I just wanted to see if my motorola g51 running android 12 could do it.

Yes, install fdroid, install termux, run termux-setup-storage. But I couldn't figure out how to get at the external device, testing with a combo usb-a/c flash drive, and voila, finally got to it after this:

With this and a sleek 1tb nvme ssd enclosure it's just charger, cable, drive cable, drive, phone, all together not much space on a desk and a nice use of one of these annoying pocket sized computers, better than any other that I know of.

I'm thinking the logical thing to do once that's set up is put LND or CLN on it and hook up a control interface to it via a tor hidden service and you pretty much should be able to just plug it in somewhere out of the way and forget about it, until somehow something breaks and you have to restart it or something.

Very interesting to me as this is something I could see an Indra relay running on, any old phone with 2gb of memory and android 6+ should be able to do this, run channels off it, it's got built in battery backup that should keep it running for half a day and you can always chain up a battery bank for longer reliablity in bad power situations. Certainly, with a 20kmwh battery bank in a backpack it would run a couple of days on mobile and wifi networks. Not really terribly useful in this way but very compact for someone like me who might need to travel and privately access the chain data.

We have discussed this very topic several times before on SN, but it seems nobody has really given it a try yet. @µð®øıð is an absolute shame, anyways, but PostmarketOS will allow us to run a full node on many mobile phones, even some from @ÞÞł€.

As for the investment on a 1TB microSD card, you could probably try with a smaller one with a pruned node if ABCore or any of the other projects previously discussed can manage that, which I guess it's highly probable (I haven't tried myself, though).

I did it with an altcoin I was working on a long time ago. I'm not sure that eMMC/SD access speed would be fast enough but maybe modern phones with a power-and-USB3 adapter and a fast flash device with over 100mb/s read/write speed would be able to do it, memory certainly wouldn't be a problem.

Only problem is since android devices changed to USB-C I haven't seen the old school style OTG cable that lets you charge and access a client device at the same time. Maybe a phone with wireless charging would let you keep it running continuously.

Android is just a cut-down version of Linux and can perfectly fine run a linux environment inside LXC containers, and you don't need root to do it. Just the issue of power-and-storage at the same time I don't know about. An old device with the USB micro socket and the old style OTG-and-charge would be able to do it but the USB interface would be a bottleneck.

blixt is apparently a full node on android