it's on izzy : https://apt.izzysoft.de/fdroid/index/apk/com.yoshi.rainyou can enable their repo on f-droid, see :https://apt.izzysoft.de/fdroid/index.phpbtw, omWeather is also a cool light one :https://f-droid.org/en/packages/org.woheller69.omweather/
512 m ram dunno, but I had an old 10 yo+ dual core / 4 gb ram laptop on arch working well, except for gaming. Just replaced it with ghostbsd, also fluid.
thanks everyone for our ideas, in the past i've used dolphin (kde) with mtp support to search files, it works but you obviously need a linux box.