Basic Editor is a lightweight editor without any ad and with only 1 permission (read/write sdcard), its source code is available at http://laughton.com/basic/programs/html/Basic%20Editor/

Basic Editor has been written with RFO BASIC! for Android, using the GW lib and compiled with the Android BASIC! Compiler.
http://rfo-basic.com
http://mougino.free.fr/rfo-basic
https://play.google.com/store/apps/details?id=com.rfo.compiler

Basic Editor registers the following file extensions: txt log ini rfo bas java xml htm html
meaning a simple tap on a file with one of these extensions in your file explorer will propose to open it with the Basic Editor.

Basic Editor natively supports light & dark modes, line grid, different font size and type (monospace, serif, sans-serif) and the usual features of your basic editors: goto line, find & replace, file information etc.

Basic Editor has a big scrollbar on the right at all times to be able to navigate through your documents with ease. You can also tap the title bar to hide the keyboard and go in read/fullscreen mode.