FakeStandby VS Simple-Calculator

And, if you use FakeStandby with screen lock disabled, you can run it without having to be worried about the battery.

If you wish to avoid burnin try Fake Standby . If latest version is not working as expected you can try previous version

Maybe this https://fakestandby.jonasbernard.de/

Found this on F-Droid: https://github.com/JonasBernard/FakeStandby

FakeStandby (version 1.3.2): Turn off your screen while keeping apps running

Here is my pick: -aurora store download apk of apps from the googleplay store. -fdroid a store for opensource apps. -aria2 to use as an advance feature rich download manager and can use to torrent. -package manager is good for when installing apkm and exporting things. -sd maid to clean unwanted folders and dead files, generally clean the phone's storage. -pdf converter might be the best app to work with pdfs. -open resources read and download books for free, also they have an audio book app too. -mindustrycool game that i like, just recommending. -vlc an ad and hassle free audio-video player. -zee archiver another choice to zarchiver. -data eraser cb phones don't really need tools like this and using without understanding is harmful to the phone. -ocr ad free and opensource ocr app. -multi filerename does what it's name says. -stealth feature rich reddit client, can be found in fdroid. -fritter twitter client. newpipe feature rich no ad youtube client. -droid splitter splits files, can be buggy sometimes but does it's job. -onlyoffice-collabora microsoft office alternative. -binary eye qr code scanner. -video transcoder transcode video. -open link with cool link tool. -touch protecter protect from accidental touches when you don't want them. -fake stand by kinda like the one above but this one saves energy. -proexpense advance miney manager. Welp thats some of my pick and sorry for the lack of upper caped characters.

I use FakeStandby "An Android app for turning the screen off while keeping apps running." for many different applications. I'd assume it would work for your purpose as well. https://github.com/JonasBernard/FakeStandby/

Simple Calculator (version 5.9.0): A beautiful calculator for quick simple calculations with smooth user interface

Simple Calculator

Simple Calculator - Do your calculations quickly (version 5.6.0): A calculator for your quick calculations.

Source: https://github.com/SimpleMobileTools/Simple-Calculator

Simplemobiletools has a camera app, you can get it from FDroid aswell

Simple Mobile Tools

APKPure app store. Or https://www.simplemobiletools.com/

If you want quality Android apps, check out my suite Simple Mobile Tools at https://www.simplemobiletools.com/ . None of them has internet access or ads, but if you want to get the latest upgrades, you need to get the Pro versions on Google Play. Or just get them on f-droid.

Simple Calculator has this